ID

VAR-201409-0366

CVE

CVE-2014-6277

TITLE

GNU Bash shell executes commands in exported functions in environment variables

DESCRIPTION

GNU Bash through 4.3 bash43-026 does not properly parse function definitions in the values of environment variables, which allows remote attackers to execute arbitrary code or cause a denial of service (uninitialized memory access, and untrusted-pointer read and write operations) via a crafted environment, as demonstrated by vectors involving the ForceCommand feature in OpenSSH sshd, the mod_cgi and mod_cgid modules in the Apache HTTP Server, scripts executed by unspecified DHCP clients, and other situations in which setting the environment occurs across a privilege boundary from Bash execution. NOTE: this vulnerability exists because of an incomplete fix for CVE-2014-6271 and CVE-2014-7169. GNU Bash 4.3 and earlier contains a command injection vulnerability that may allow remote code execution. This vulnerability CVE-2014-6271 and CVE-2014-7169 Vulnerability due to insufficient fix for.Arbitrary code execution or denial of service by a third party through a crafted environment ( Uninitialized memory access and untrusted pointer read and write operations ) There is a possibility of being put into a state. An attacker can exploit this issue to execute arbitrary code within the context of the affected application. Failed exploit attempts will result in a denial-of-service condition. -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Note: the current version of the following document is available here: https://h20564.www2.hp.com/portal/site/hpsc/public/kb/ docDisplay?docId=emr_na-c04558068 SUPPORT COMMUNICATION - SECURITY BULLETIN Document ID: c04558068 Version: 1 HPSBMU03246 rev.1 - HP Insight Control for Linux Central Management Server Pre-boot Execution Environment running Bash Shell, Multiple Vulnerabilities NOTICE: The information in this Security Bulletin should be acted upon as soon as possible. Release Date: 2015-02-02 Last Updated: 2015-02-02 Potential Security Impact: Multiple vulnerabilities Source: Hewlett-Packard Company, HP Software Security Response Team VULNERABILITY SUMMARY Potential security vulnerabilities have been identified with HP Insight Control for Linux Central Management Server Pre-boot Execution Environment that could be exploited remotely resulting in Denial of Service (DoS), disclosure of information, and other vulnerabilities. References: CVE-2014-6271 CVE-2014-6277 CVE-2014-6278 CVE-2014-7169 CVE-2014-7186 CVE-2014-7187 CVE-2014-7196 SSRT101742 SUPPORTED SOFTWARE VERSIONS*: ONLY impacted versions are listed. HP Insight Control for Linux Central Management Server Pre-boot Execution Environment running Bash Shell BACKGROUND CVSS 2.0 Base Metrics =========================================================== Reference Base Vector Base Score CVE-2014-6271 (AV:N/AC:L/Au:N/C:C/I:C/A:C) 10.0 CVE-2014-6277 (AV:N/AC:L/Au:N/C:C/I:C/A:C) 10.0 CVE-2014-6278 (AV:N/AC:L/Au:N/C:C/I:C/A:C) 10.0 CVE-2014-7169 (AV:N/AC:L/Au:N/C:C/I:C/A:C) 10.0 CVE-2014-7186 (AV:N/AC:L/Au:N/C:C/I:C/A:C) 10.0 CVE-2014-7187 (AV:N/AC:L/Au:N/C:C/I:C/A:C) 10.0 CVE-2014-7196 (AV:N/AC:L/Au:N/C:C/I:C/A:C) 10.0 =========================================================== Information on CVSS is documented in HP Customer Notice: HPSN-2008-002 RESOLUTION HP has provided the following instructions to resolve these vulnerabilities. Follow these steps to update the HP Insight Control for Linux Central Management Server Pre-boot Execution Environment: NOTE: The following procedure updates the bash shell on the Linux Pre-boot Execution Environment. Please update the Bash shell version on the HP Insight Control for Linux Central Management Server also. 1. On the Production RHEL 6.2 OS: a. Prepare temporary directory for Bash update software: # mkdir -p $HOME/tmp/bash # cd $HOME/tmp/bash # pwd <home directory>/tmp/bash b. Download the file 'bash-4.1.2-15.el6_4.2.i686.rpm' for Insight Control for Linux Red Hat 6.2 i386 from https://rhn.redhat.com/errata/RHSA-2014-1311.html to the temporary directory '$HOME/tmp/bash'. c. Extract the Bash update software package. # rpm2cpio bash-4.1.2-15.el6_4.2.i686.rpm| cpio -idmv d. Verify the version of the Bash update software: # ./bin/bash --version GNU bash, version 4.1.2(1)-release (i686-redhat-linux-gnu) e. Verify version dependencies: # ldd ./bin/bash linux-gate.so.1 => (0x008a7000) libtinfo.so.5 => /lib/libtinfo.so.5 (0x00459000) libdl.so.2 => /lib/libdl.so.2 (0x002c0000) libc.so.6 => /lib/libc.so.6 (0x0012e000) /lib/ld-linux.so.2 (0x00108000) f. Create archive file from '/lib' to copy and install on the Insight Control for Linux Central Management Server Pre-boot Execution Environment system: # mkdir $HOME/tmp/lib # cd /lib # cp * $HOME/tmp/lib # cd $HOME/tmp # pwd <home directory>/tmp # tar cvf bash_lib.tar * 2. Download the new archive file '$HOME/tmp/bash_lib.tar' from the Production RHEL 6.2 OS system to the Insight Control for Linux Central Management Server Pre-boot Execution Environment system. 3. On the HP Insight Control for Linux Central Managment Server Pre-boot Execution Environment system: a. Create a temporary folder for the toolkit and copy the toolkit there : # mkdir -p $HOME/tmp/temp-toolkit # cp /usr/share/systemimager/boot/i386/standard/toolkit.tar.gz $HOME/tmp/temp-toolkit b. Extract the file 'toolkit.tar.gz' into the temporary folder: # cd $HOME/tmp/temp-toolkit # tar zxvf toolkit.tar.gz # mv $HOME/tmp/temp-toolkit/toolkit.tar.gz /tmp c. Verify the version of the toolkit Bash: # $HOME/tmp/temp-toolkit/bin/bash --version GNU bash, version 3.2.0(1)-release (i386-pc-linux-gnu) Copyright (C) 2005 Free Software Foundation, Inc. d. Verify dependencies versions: # ldd $HOME/tmp/temp-toolkit/bin/bash linux-gate.so.1 => (0xffffe000) libtermcap.so.2 => /lib/libtermcap.so.2 (0xf7f8c000) libdl.so.2 => /lib/libdl.so.2 (0x008bf000) libc.so.6 => /lib/libc.so.6 (0x00777000) /lib/ld-linux.so.2 (0x00755000) e. Extract the archive 'bash_lib.tar' to directory '$HOME/tmp/bash_lib' . Then copy the bash binary and the library files to their respective locations: # tar xvf $HOME/tmp/bash_lib # cp $HOME/tmp/bash_lib/bash/bash $HOME/tmp/temp-toolkit/bin # cp $HOME/tmp/bash_lib/lib/* $HOME/tmp/temp-toolkit/lib f. Create the updated toolkit gzipped archive file and place in /usr/share/systemimager/boot/i386/standard # tar czvf toolkit.tar.gz * # cp toolkit.tar.gz /usr/share/systemimager/boot/i386/standard HISTORY Version:1 (rev.1) - 2 February 2015 Initial release Third Party Security Patches: Third party security patches that are to be installed on systems running HP software products should be applied in accordance with the customer's patch management policy. Support: For issues about implementing the recommendations of this Security Bulletin, contact normal HP Services support channel. For other issues about the content of this Security Bulletin, send e-mail to security-alert@hp.com. Report: To report a potential security vulnerability with any HP supported product, send Email to: security-alert@hp.com Subscribe: To initiate a subscription to receive future HP Security Bulletin alerts via Email: http://h41183.www4.hp.com/signup_alerts.php?jumpid=hpsc_secbulletins Security Bulletin Archive: A list of recently released Security Bulletins is available here: https://h20564.www2.hp.com/portal/site/hpsc/public/kb/secBullArchive/ Software Product Category: The Software Product Category is represented in the title by the two characters following HPSB. 3C = 3COM 3P = 3rd Party Software GN = HP General Software HF = HP Hardware and Firmware MP = MPE/iX MU = Multi-Platform Software NS = NonStop Servers OV = OpenVMS PI = Printing and Imaging PV = ProCurve ST = Storage Software TU = Tru64 UNIX UX = HP-UX Copyright 2015 Hewlett-Packard Development Company, L.P. Hewlett-Packard Company shall not be liable for technical or editorial errors or omissions contained herein. The information provided is provided "as is" without warranty of any kind. To the extent permitted by law, neither HP or its affiliates, subcontractors or suppliers will be liable for incidental,special or consequential damages including downtime cost; lost profits; damages relating to the procurement of substitute products or services; or damages for loss of data, or software restoration. The information in this document is subject to change without notice. Hewlett-Packard Company and the names of Hewlett-Packard products referenced herein are trademarks of Hewlett-Packard Company in the United States and other countries. Other product and company names mentioned herein may be trademarks of their respective owners. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.13 (GNU/Linux) iEYEARECAAYFAlTP2EgACgkQ4B86/C0qfVnMkQCg8yH4xRTp9ahC3s4vDiCBmKiV JTwAoPl3SC09DPRWwo1zluDWFF1OfMtA =w7+V -----END PGP SIGNATURE----- . Note: All versions of HP Thin Pro and HP Smart Zero Core operating systems prior to version 5.1.0 are affected by these vulnerabilities. Following is a complete list of affected operating systems and Hardware Platforms Affected. HP ThinPro: HP ThinPro 5.0 (released June 2014) HP ThinPro 4.4 (released November 2013) HP ThinPro 4.3 (released June 2013) HP ThinPro 4.2 (released November 2012) HP ThinPro 4.1 (released March 2012) HP ThinPro 3.2 (released November 2010) HP ThinPro 3.1 (released June 2010) HP ThinPro 3.0 (released November 2009) HP ThinPro 2.0 (released 2009) HP ThinPro 1.5 (released 2009) HP ThinPro 1.0 (released 2008) HP Smart Zero Core: HP Smart Zero Core 5.0 (released June 2014) HP Smart Zero Core 4.4 (released November 2013) HP Smart Zero Core 4.3 (released June 2013) HP Smart Zero Core 4.2 (released November 2012) HP Smart Zero Core 4.1 (released March 2012) HP Smart Zero Core 4.0 (released March 2011) Hardware Platforms Affected: HP t620 PLUS Flexible Quad Core Thin Client HP t620 Flexible Dual Core Thin Client HP t620 PLUS Flexible Dual Core Thin Client HP t620 Flexible Quad Core Thin Client HP t520 Flexible Thin Client HP t505 Flexible Thin Client HP t510 Flexible Thin Client HP t410 All-in-One 18.5 RFX/HDX Smart ZC HP t410 Smart Zero Client HP t610 PLUS Flexible Thin Client HP t610 Flexible Thin Client HP t5565 Thin Client HP t5565z Smart Client BACKGROUND CVSS 2.0 Base Metrics =========================================================== Reference Base Vector Base Score CVE-2014-6271 (AV:N/AC:L/Au:N/C:C/I:C/A:C) 10 CVE-2104-6277 (AV:N/AC:L/Au:N/C:C/I:C/A:C) 10 CVE-2104-6278 (AV:N/AC:L/Au:N/C:C/I:C/A:C) 10 CVE-2014-7169 (AV:N/AC:L/Au:N/C:C/I:C/A:C) 10 CVE-2014-7186 (AV:N/AC:L/Au:N/C:C/I:C/A:C) 10 CVE-2014-7187 (AV:N/AC:L/Au:N/C:C/I:C/A:C) 10 =========================================================== Information on CVSS is documented in HP Customer Notice: HPSN-2008-002 RESOLUTION HP has released the following software updates to resolve these vulnerabilities. Product Affected Product Versions Patch Status HP ThinPro and HP Smart Zero Core (X86) v5.1.0 and above No update required; the Bash shell patch is incorporated into the base image. Note: If you participated in the ThinPro 5.1.0 beta program then upgrade to the release version as soon as it becomes available. HP ThinPro and HP Smart Zero Core (x86) v5.0.x A component update is currently available through Easy Update as: SecurityUpdate-Shellshock-2.0-all-5.0-x86.xar . The update can be also downloaded directly from HP as part of softpaq sp69382 at the following address: ftp://ftp.hp.com/pub/softpaq/sp69001-69500/sp69382.exe HP ThinPro and HP Smart Zero Core (x86) v4.4.x A component update is currently available through Easy Update as: SecurityUpdate-Shellshock-2.0-all-4.4-x86.xar . The update can be also downloaded directly from HP as part of softpaq sp69382 at the following address: ftp://ftp.hp.com/pub/softpaq/sp69001-69500/sp69382.exe HP ThinPro and HP Smart Zero Core (ARM) v4.4.x A component update is currently available through Easy Update as: SecurityUpdate-Shellshock-2.0-all-4.4-arm.xar . The update can be also downloaded directly from HP as part of softpaq sp69382 at the following address: ftp://ftp.hp.com/pub/softpaq/sp69001-69500/sp69382.exe HP ThinPro and HP Smart Zero Core (X86) v4.1, v4.2, and v4.3 A component update is currently available through Easy Update as: SecurityUpdate-Shellshock-2.0-all-4.1-4.2-4.3-x86.xar . The update can be also downloaded directly from HP as part of softpaq sp69382 at the following address: ftp://ftp.hp.com/pub/softpaq/sp69001-69500/sp69382.exe HP ThinPro and HP Smart Zero Core (ARM) v4.1, v4.2, and v4.3 A component update is currently available through Easy Update as: SecurityUpdate-Shellshock-2.0-all-4.1-4.2-4.3-arm.xar . The update can be also downloaded directly from HP as part of softpaq sp69382 at the following address: ftp://ftp.hp.com/pub/softpaq/sp69001-69500/sp69382.exe HP ThinPro and HP Smart Zero Core (X86) v3.1, v3.2, and v3.3 Download softpaq sp69382 from: ftp://ftp.hp.com/pub/softpaq/sp69001-69500/sp69382.exe which contains an update package as: bash_4.1-3+deb6u2_i386.deb . HP ThinPro and HP Smart Zero Core (ARM) v3.1, v3.2, and v3.3 Download softpaq sp69382 from: ftp://ftp.hp.com/pub/softpaq/sp69001-69500/sp69382.exe which contains an update package as: bash_4.1-3+deb6u2_armel.deb . This vulnerability allows users that have been granted access to a shell script to escalate privilege and execute unrestricted commands at the same security level as the Bash script. Good morning! This is kinda long. == Background == If you are not familiar with the original bash function export vulnerability (CVE-2014-6271), you may want to have a look at this article: http://lcamtuf.blogspot.com/2014/09/quick-notes-about-bash-bug-its-impact.html Well, long story short: the initial maintainer-provided patch for this issue [1] (released on September 24) is *conclusively* broken. After nagging people to update for a while [5] [7], I wanted to share the technical details of two previously non-public issues which may be used to circumvent the original patch: CVE-2014-6277 and CVE-2014-6278. Note that the issues discussed here are separate from the three probably less severe problems publicly disclosed earlier on: Tavis' limited-exploitability EOL bug (CVE-2014-7169) and two likely non-exploitable one-off issues found by Florian Weimer and Todd Sabin (CVE-2014-7186 and CVE-2014-7187). == Required actions == If you have installed just the September 24 patch [1], or that and the follow-up September 26 patch for CVE-2014-7169 [2], you are likely still vulnerable to RCE and need to update ASAP, as discussed in [5]. You are safe if you have installed the unofficial function prefix patch from Florian Weimer [3], or its upstream variant released on September 28 [4]. The patch does not eliminate the problems, but shields the underlying parser from untrusted inputs under normal circumstances. Note: over the past few days, Florian's patch has been picked up by major Linux distros (Red Hat, Debian, SUSE, etc), so there is a reasonable probability that you are in good shape. To test, execute this command from within a bash shell: foo='() { echo not patched; }' bash -c foo If you see "not patched", you probably want upgrade immediately. If you see "bash: foo: command not found", you're OK. == Vulnerability details: CVE-2014-6277 (the more involved one) == The following function definition appearing in the value of any environmental variable passed to bash will lead to an attempt to dereference attacker-controlled pointers (provided that the targeted instance of bash is protected only with the original patches [1][2] and does not include Florian's fix): () { x() { _; }; x() { _; } <<a; } A more complete example leading to a deref of 0x41414141 would be: HTTP_COOKIE="() { x() { _; }; x() { _; } <<`perl -e '{print "A"x1000}'`; }" bash -c : bash[25662]: segfault at 41414141 ip 00190d96 sp bfbe6354 error 4 in libc-2.12.so[110000+191000] (If you are seeing 0xdfdfdfdf, see note later on). The issue is caused by an uninitialized here_doc_eof field in a REDIR struct originally created in make_redirection(). The initial segv will happen due to an attempt to read and then copy a string to a new buffer through a macro that expands to: strcpy (xmalloc (1 + strlen (redirect->here_doc_eof)), (redirect->here_doc_eof)) This appears to be exploitable in at least one way: if here_doc_eof is chosen by the attacker to point in the vicinity of the current stack pointer, the apparent contents of the string - and therefore its length - may change between stack-based calls to xmalloc() and strcpy() as a natural consequence of an attempt to pass parameters and create local variables. Such a mid-macro switch will result in an out-of-bounds write to the newly-allocated memory. A simple conceptual illustration of this attack vector would be: -- snip! -- char* result; int len_alloced; main(int argc, char** argv) { /* The offset will be system- and compiler-specific */; char* ptr = &ptr - 9; result = strcpy (malloc(100 + (len_alloced = strlen(ptr))), ptr); printf("requested memory = %d\n" "copied text = %d\n", len_alloced + 1, strlen(result) + 1); } -- snip! -- When compiled with the -O2 flag used for bash, on one test system, this produces: requested memory = 2 copied text = 28 This can lead to heap corruption, with multiple writes possible per payload by simply increasing the number of malformed here-docs. The consequences should be fairly clear. [ There is also a latter call to free() on here_doc_eof in dispose_cmd.c, but because of the simultaneous discovery of the much simpler bug '78 discussed in the next section, I have not spent a whole lot of time trying to figure out how to get to that path. ] Perhaps notably, the ability to specify attacker-controlled addresses hinges on the state of --enable-bash-malloc and --enable-mem-scramble compile-time flags; if both are enabled, the memory returned by xmalloc() will be initialized to 0xdf, making the prospect of exploitation more speculative (essentially depending on whether the stack or any other memory region can be grown to overlap with 0xdfdfdfdf). That said, many Linux distributions disable one or both flags and are vulnerable out-of-the-box. It is also of note that relatively few distributions compile bash as PIE, so there is little consolation to be found in ASLR. Similarly to the original vulnerability, this issue can be usually triggered remotely through web servers such as Apache (provided that they invoke CGI scripts or PHP / Python / Perl / C / Java servlets that rely on system() or popen()-type libcalls); through DHCP clients; and through some MUAs and MTAs. For a more detailed discussion of the exposed attack surface, refer to [6]. == Vulnerability details: CVE-2014-6278 (the "back to the '90s" one) == The following function definition appearing in the value of any environmental variable passed to bash 4.2 or 4.3 will lead to straightforward put-your-command-here RCE (again, provided that the targeted instance is not protected with Florian's patch): () { _; } >_[$($())] { echo hi mom; id; } A complete example looks like this: HTTP_COOKIE='() { _; } >_[$($())] { echo hi mom; id; }' bash -c : ...or: GET /some/script.cgi HTTP/1.0 User-Agent: () { _; } >_[$($())] { id >/tmp/hi_mom; } Note that the PoC does not work as-is in more ancient versions of bash, such as 2.x or 3.x; it might have been introduced with xparse_dolparen() starting with bash 4.2 patch level 12 few years back, but I have not investigated this in a lot of detail. Florian's patch is strongly recommended either way. The attack surface through which this flaw may be triggered is roughly similar to that for CVE-2014-6277 and the original bash bug [6]. == Additional info == Both of these issues were identified in an automated fashion with american fuzzy lop: https://code.google.com/p/american-fuzzy-lop The out-of-the-box fuzzer was seeded with a minimal valid function definition ("() { foo() { foo; }; >bar; }") and allowed to run for a couple of hours on a single core. In addition to the issues discussed above, the fuzzer also hit three of the four previously-reported CVEs. I initially shared the findings privately with vendors, but because of the intense scrutiny that this codebase is under, the ease of reproducing these results with an open-source fuzzer, and the now-broad availability of upstream mitigations, there seems to be relatively little value in continued secrecy. == References == [1] http://ftp.gnu.org/gnu/bash/bash-4.3-patches/bash43-025 [2] http://ftp.gnu.org/gnu/bash/bash-4.3-patches/bash43-026 [3] http://www.openwall.com/lists/oss-security/2014/09/25/13 [4] http://ftp.gnu.org/gnu/bash/bash-4.3-patches/bash43-027 [5] http://lcamtuf.blogspot.com/2014/09/bash-bug-apply-unofficial-patch-now.html [6] http://lcamtuf.blogspot.com/2014/09/quick-notes-about-bash-bug-its-impact.html [7] http://www.pcworld.com/article/2688932/improved-patch-tackles-new-shellshock-attack-vectors.html PS. There are no other bugs in bash. --------- FOLLOW UP ----------- Date: Wed, 01 Oct 2014 07:32:57 -0700 From fulldisclosure-bounces@seclists.org Wed Oct 1 14:37:33 2014 From: Paul Vixie <paul@redbarn.org> To: Michal Zalewski <lcamtuf@coredump.cx> Cc: "fulldisclosure@seclists.org" <fulldisclosure@seclists.org> Subject: Re: [FD] the other bash RCEs (CVE-2014-6277 and CVE-2014-6278) michal, thank you for your incredibly informative report here. i have a minor correction. > Michal Zalewski <mailto:lcamtuf@coredump.cx> > Wednesday, October 01, 2014 7:21 AM > ... > > Note: over the past few days, Florian's patch has been picked up by > major Linux distros (Red Hat, Debian, SUSE, etc), so there is a > reasonable probability that you are in good shape. To test, execute > this command from within a bash shell: > > foo='() { echo not patched; }' bash -c foo this command need not be executed from within bash. the problem occurs when bash is run by the command, and the shell that runs the command can be anything. for example, on a system where i have deliberately not patched bash, where sh is "ash" (almquist shell): > $ foo='() { echo not patched; }' bash -c foo > not patched here's me testing it from within tcsh: > % env foo='() { echo not patched; }' bash -c foo > not patched > % (setenv foo '() { echo not patched; }'; bash -c foo) > not patched this is a minor issue, but i've found in matters of security bug reports, tests, and discussions, that any minor matter can lead to deep misunderstanding. thanks again for your excellent report, and your continuing work on this issue. vixie . No other firmware stream updates are planned beyond the NX-OS 5.x and 6.x versions listed below for the MDS products. This software versions 6.2(9a) has included the fixes for the vulnerability in HP StoreFabric C-series MDS switches which currently supporting NX-OS 6.X releases. This software version 5.2(8e) has included the fix for the vulnerability in HP C-series MDS switches which currently supporting NX-OS 5.X releases. HP is continuing to actively work on software updates to resolve the vulnerability in HP C-series Nexus 5k switches. This bulletin will be revised when these updates become available. MITIGATION INFORMATION If updating to a NX-OS version containing the fix is not currently possible, HP recommends the following steps to reduce the risk of this vulnerability: The "ssh" or "telnet" features may be disabled by the admin user. All MDS and Nexus 5K switches can function in this configuration. Access is available through the console port

AFFECTED PRODUCTS

CVSS

PROBLEMTYPE DATA

THREAT TYPE

network

TYPE

Design Error

CONFIGURATIONS

EXPLOIT AVAILABILITY

PATCH

EXTERNAL IDS

REFERENCES

CREDITS

HP

SOURCES

LAST UPDATE DATE

2025-05-01T20:51:02.456000+00:00

SOURCES UPDATE DATE

SOURCES RELEASE DATE