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Date: Thu, 18 Apr 2024 18:42:42 +0200
From: Solar Designer <>
Subject: Re: The GNU C Library security advisories update for 2024-04-17: GLIBC-SA-2024-0004/CVE-2024-2961: ISO-2022-CN-EXT: fix out-of-bound writes when writing escape sequence

On Wed, Apr 17, 2024 at 02:36:02PM -0300, Adhemerval Zanella Netto wrote:
> GLIBC-SA-2024-0004:
> ===================
> ISO-2022-CN-EXT: fix out-of-bound writes when writing escape sequence
> The iconv() function in the GNU C Library versions 2.39 and older may
> overflow the output buffer passed to it by up to 4 bytes when converting
> strings to the ISO-2022-CN-EXT character set, which may be used to
> crash an application or overwrite a neighbouring variable.
> ISO-2022-CN-EXT uses escape sequences to indicate character set changes
> (as specified by RFC 1922).  While the SOdesignation has the expected
> bounds checks, neither SS2designation nor SS3designation have its;
> allowing a write overflow of 1, 2, or 3 bytes with fixed values:
> '$+I', '$+J', '$+K', '$+L', '$+M', or '$*H'.
> CVE-Id: CVE-2024-2961
> Public-Date: 2024-04-17
> Vulnerable-Commit: 755104edc75c53f4a0e7440334e944ad3c6b32fc (2.1.93-169)
> Fix-Commit: f9dc609e06b1136bb0408be9605ce7973a767ada (2.40)
> Fix-Commit: 31da30f23cddd36db29d5b6a1c7619361b271fb4 (2.39-31)
> Fix-Commit: e1135387deded5d73924f6ca20c72a35dc8e1bda (2.38-66)
> Fix-Commit: 89ce64b269a897a7780e4c73a7412016381c6ecf (2.37-89)
> Fix-Commit: 4ed98540a7fd19f458287e783ae59c41e64df7b5 (2.36-164)
> Fix-Commit: 36280d1ce5e245aabefb877fe4d3c6cff95dabfa (2.35-315)
> Fix-Commit: a8b0561db4b9847ebfbfec20075697d5492a363c (2.34-459)
> Fix-Commit: ed4f16ff6bed3037266f1fa682ebd32a18fce29c (2.33-263)
> Fix-Commit: 682ad4c8623e611a971839990ceef00346289cc9 (2.32-140)
> Reported-By: Charles Fol

I hope Charles will share further detail with oss-security in due time,
but meanwhile his upcoming OffensiveCon talk abstract reveals a bit:

> Abstract
> A few months ago, I stumbled upon a 24 years old buffer overflow in the
> glibc. Despite being reachable in multiple well-known libraries or
> programs, it proved rarely exploitable. Indeed, this was not a foos bug:
> with hard-to-achieve preconditions, it did not even provide a nice
> primitive. On PHP however, it lead to amazing results: a new
> exploitation technique that affects the whole PHP ecosystem, and the
> compromission of several applications.
> This talk will first walk you through the discovery of the bug and its
> limitations, before describing the conception of several remote binary
> PHP exploits, and through them offer unique insight in the internal of
> the engine of the web language, and the difficulties one faces when
> exploiting it.
> Charles Fol, also known as cfreal, is a security researcher at LEXFO /
> AMBIONICS. He has discovered remote code execution vulnerabilities
> targeting renowned CMS and frameworks such as Drupal, Magento, Symfony
> or Laravel, but also enjoys binary exploitation, to escalate privileges
> (Apache, PHP-FPM) or compromise security solutions (DataDog's Sqreen,
> Fortinet SSL VPN, Watchguard). He is the creator for PHPGGC, the go-to
> tool to exploit PHP deserialization, and an expert in PHP internals.

The event is on May 10-11th, so in 3 weeks from now.


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