-----BEGIN PGP SIGNED MESSAGE-----
AUSCERT External Security Bulletin Redistribution
Multiple vulnerabilities in the execve system call
29 August 2014
AusCERT Security Bulletin Summary
Operating System: NetBSD
Impact/Access: Denial of Service -- Existing Account
- --------------------------BEGIN INCLUDED TEXT--------------------
- -----BEGIN PGP SIGNED MESSAGE-----
NetBSD Security Advisory 2014-009
Topic: Multiple vulnerabilities in the execve system call
Version: NetBSD-current: source prior to Fri, Feb 14th 2014
NetBSD 6.1 - 6.1.3: affected
NetBSD 6.1.4: not affected
NetBSD 6.0 - 6.0.4: affected
NetBSD 6.0.5: not affected
NetBSD 5.1 - 5.1.4: not affected
NetBSD 5.2 - 5.2.2: not affected
Severity: Local DoS
Fixed: NetBSD-current: Fri, Feb 14th 2014
NetBSD-6-0 branch: Fri, Feb 14th 2014
NetBSD-6-1 branch: Fri, Feb 14th 2014
NetBSD-6 branch: Fri, Feb 14th 2014
Teeny versions released later than the fix date will contain the fix.
Please note that NetBSD releases prior to 5.1 are no longer supported.
It is recommended that all users upgrade to a supported release.
The execve system call is affected by two vulnerabilities:
1) A memory leak in the kernel could cause a local (un)privileged user
to use up kernel memory via a bogus ELF binary, and thus to freeze - or
eventually panic - the system.
2) A bug in the kernel could lead to a use-after-free condition when
loading a binary or a script, which would allow a local (un)privileged
user to crash the system.
1) When trying to execute an ELF binary, the kernel looks up the
corresponding "interpreter" (in case of native dynamic ELF binaries: the
dynamic linker ld.elf_so). If this interpreter cannot be accessed
appropriately, or if it is bogus, a structure allocated to hold special
information on this interpreter was not freed.
If a standard toolchain is installed, a local user can easily create
such broken binaries by passing the -dynamic-linker switch to the linker.
2) When executing a binary via execve(), the kernel computes the new
user stack size, and returns an error if this size exceeds the maximum
architecture-defined stack size or the maximum stack size allowed by the
calling process through rlimit. However, the variable in charge of hold-
ing the error code returned was not properly initialised, causing the
kernel to keep setting up the new process environment and use data that
was already freed.
Both the new stack size and the rlimit stack size are approximately
user-controllable, which makes it easy to trigger from a local user.
Solutions and Workarounds
For all NetBSD versions, you need to obtain fixed kernel sources,
rebuild and install the new kernel, and reboot the system.
The fixed source may be obtained from the NetBSD CVS repository.
The following instructions briefly summarise how to upgrade your
kernel. In these instructions, replace:
ARCH with your architecture (from uname -m),
KERNCONF with the name of your kernel configuration file and
VERSION with the file version below
File versions containing the fixes:
FILE HEAD netbsd-6 netbsd-6-1 netbsd-6-0
- - ---- ---- -------- ---------- ----------
1.55 126.96.36.199 188.8.131.52.6.1 184.108.40.206.4.1
1.403 1.339.2.9 1.3220.127.116.11.2 1.318.104.22.168.3
To update from CVS, re-build, and re-install the kernel:
# cd src
# cvs update -d -P -r VERSION sys/kern/exec_elf.c
# cvs update -d -P -r VERSION sys/kern/kern_exec.c
# ./build.sh kernel=KERNCONF
# mv /netbsd /netbsd.old
# cp sys/arch/ARCH/compile/obj/KERNCONF/netbsd /netbsd
# shutdown -r now
For more information on how to do this, see:
Thanks to Maxime Villard, who found the issues and provided fixes.
2014-08-27 Initial release
Advisories may be updated as new information becomes available.
The most recent version of this advisory (PGP signed) can be found at
Information about NetBSD and NetBSD security can be found at
http://www.NetBSD.org/ and http://www.NetBSD.org/Security/ .
Copyright 2014, The NetBSD Foundation, Inc. All Rights Reserved.
Redistribution permitted only in full, unmodified form.
$NetBSD: NetBSD-SA2014-009.txt,v 1.1 2014/08/27 00:19:19 tonnerre Exp $
- -----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
- -----END PGP SIGNATURE-----
- --------------------------END INCLUDED TEXT--------------------
You have received this e-mail bulletin as a result of your organisation's
registration with AusCERT. The mailing list you are subscribed to is
maintained within your organisation, so if you do not wish to continue
receiving these bulletins you should contact your local IT manager. If
you do not know who that is, please send an email to email@example.com
and we will forward your request to the appropriate person.
NOTE: Third Party Rights
This security bulletin is provided as a service to AusCERT's members. As
AusCERT did not write the document quoted above, AusCERT has had no control
over its content. The decision to follow or act on information or advice
contained in this security bulletin is the responsibility of each user or
organisation, and should be considered in accordance with your organisation's
site policies and procedures. AusCERT takes no responsibility for consequences
which may arise from following or acting on information or advice contained in
this security bulletin.
NOTE: This is only the original release of the security bulletin. It may
not be updated when updates to the original are made. If downloading at
a later date, it is recommended that the bulletin is retrieved directly
from the author's website to ensure that the information is still current.
Contact information for the authors of the original document is included
in the Security Bulletin above. If you have any questions or need further
information, please contact them directly.
Previous advisories and external security bulletins can be retrieved from:
Australian Computer Emergency Response Team
The University of Queensland
Internet Email: firstname.lastname@example.org
Facsimile: (07) 3365 7031
Telephone: (07) 3365 4417 (International: +61 7 3365 4417)
AusCERT personnel answer during Queensland business hours
which are GMT+10:00 (AEST).
On call after hours for member emergencies only.
-----BEGIN PGP SIGNATURE-----
-----END PGP SIGNATURE-----