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Date: Wed, 18 Apr 2012 11:06:42 -0600
From: Kurt Seifried <kseifried@...hat.com>
To: oss-security@...ts.openwall.com
CC: Rich Felker <dalias@...ifal.cx>, musl@...ts.openwall.com
Subject: Re: Stack-based buffer overflow in musl libc 0.8.7
 and earlier

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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

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