Stack-based buffer overflow in musl libc 0.8.7 and earlier

Stack-based buffer overflow in musl libc 0.8.7 and earlier

[Rich Felker]

Name: Stack-based buffer overflow in musl libc 0.8.7 and earlier
Software: musl 0.8.7 and earlier
Software link:  http://www.etalabs.net/musl
Vulnerability Type: Buffer overflow
Severity: Critical

Software Description:

musl is an implementation of the C/POSIX standard library for
Linux-based systems. musl aims to be lightweight, fast, simple, free,
and correct in the sense of standards-conformance and safety, and to
meet requirements ranging from embedded systems and initrd images to
desktop workstations, mobile devices, and high-load servers. Several
build-from-source mini-distributions use musl as their C library.

Vulnerability Details:

musl's implementation of [v]fprintf swaps in a temporary FILE buffer
on the stack when writing to unbuffered streams such as stderr. Under
certain conditions where the buffer end pointer has already been set
to the address of the internal degenerate buffer prior to the call to
[v]fprintf, stdio internals can fail to bound access to the temporary
buffer. Large writes will then overflow the temporary buffer and
clobber stack contents, including potentially the return address. Any
program linked to musl which includes potentially-large data from
untrusted sources in its output to stderr or other unbuffered streams
is affected.

Solution:

The vulnerability has been fixed in git, and the fix is to be included
in the upcoming 0.8.8 release. A patch which applies cleanly to all
recent releases is available on the musl mailing list:

http://www.openwall.com/lists/musl/2012/04/17/1

Credits:

This vulnerability was discovered and fixed by the author (myself,
Rich Felker) while debugging a crash occurring in test code written
for musl by Luka Marčetić as part of GSoC 2011.

Re: Stack-based buffer overflow in musl libc 0.8.7 and earlier

[Kurt Seifried]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 04/18/2012 12:32 AM, Rich Felker wrote:
> Name: Stack-based buffer overflow in musl libc 0.8.7 and earlier 
> Software: musl 0.8.7 and earlier Software link:
> http://www.etalabs.net/musl Vulnerability Type: Buffer overflow 
> Severity: Critical
> 
> Software Description:
> 
> musl is an implementation of the C/POSIX standard library for 
> Linux-based systems. musl aims to be lightweight, fast, simple,
> free, and correct in the sense of standards-conformance and safety,
> and to meet requirements ranging from embedded systems and initrd
> images to desktop workstations, mobile devices, and high-load
> servers. Several build-from-source mini-distributions use musl as
> their C library.
> 
> Vulnerability Details:
> 
> musl's implementation of [v]fprintf swaps in a temporary FILE
> buffer on the stack when writing to unbuffered streams such as
> stderr. Under certain conditions where the buffer end pointer has
> already been set to the address of the internal degenerate buffer
> prior to the call to [v]fprintf, stdio internals can fail to bound
> access to the temporary buffer. Large writes will then overflow the
> temporary buffer and clobber stack contents, including potentially
> the return address. Any program linked to musl which includes
> potentially-large data from untrusted sources in its output to
> stderr or other unbuffered streams is affected.
> 
> Solution:
> 
> The vulnerability has been fixed in git, and the fix is to be
> included in the upcoming 0.8.8 release. A patch which applies
> cleanly to all recent releases is available on the musl mailing
> list:
> 
> http://www.openwall.com/lists/musl/2012/04/17/1
> 
> Credits:
> 
> This vulnerability was discovered and fixed by the author (myself, 
> Rich Felker) while debugging a crash occurring in test code
> written for musl by Luka Marčetić as part of GSoC 2011.

Please use CVE-2012-2114 for this issue.

- -- 
Kurt Seifried Red Hat Security Response Team (SRT)
PGP: 0x5E267993 A90B F995 7350 148F 66BF 7554 160D 4553 5E26 7993

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.12 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/
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=Zkg2
-----END PGP SIGNATURE-----