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Message-ID: <s9890o96-qqoo-7536-q2pp-po275s8rsnon@unkk.fr>
Date: Wed, 24 Jul 2024 08:34:35 +0200 (CEST)
From: Daniel Stenberg <daniel@...x.se>
To: curl security announcements -- curl users <curl-users@...ts.haxx.se>,
curl-announce@...ts.haxx.se, libcurl hacking <curl-library@...ts.haxx.se>,
oss-security@...ts.openwall.com
Subject: [SECURITY ADVISORY] curl: CVE-2024-6197: freeing stack buffer in
utf8asn1str
freeing stack buffer in utf8asn1str
===================================
Project curl Security Advisory, July 24th 2024 -
[Permalink](https://curl.se/docs/CVE-2024-6197.html)
VULNERABILITY
-------------
libcurl's ASN1 parser has this utf8asn1str() function used for parsing an
ASN.1 UTF-8 string. It can detect an invalid field and return error.
Unfortunately, when doing so it also invokes `free()` on a 4 byte local stack
buffer.
Most modern malloc implementations detect this error and immediately abort.
Some however accept the input pointer and add that memory to its list of
available chunks. This leads to the overwriting of nearby stack memory. The
content of the overwrite is decided by the `free()` implementation; likely to
be memory pointers and a set of flags.
The most likely outcome of exploting this flaw is a crash, although it cannot
be ruled out that more serious results can be had in special circumstances.
INFO
----
The vulnerable code path can be triggered by a malicious server offering an
especially crafted TLS certificate.
This bug was introduced in a code refactor shipped in the curl 8.6.0 release
and is considered a *C mistake* (likely to have been avoided had we not been
using C).
This flaw also affects the curl command line tool.
The Common Vulnerabilities and Exposures (CVE) project has assigned the name
CVE-2024-6197 to this issue.
CWE-590: Free of Memory not on the Heap
Severity: Medium
AFFECTED VERSIONS
-----------------
The vulnerable code can only be reached when curl is built to use GnuTLS,
wolfSSL, Schannel or Secure Transport. Builds using other TLS backends are not
vulnerable.
- Affected versions: curl 8.6.0 to and including 8.8.0
- Not affected versions: curl < 8.6.0 and >= 8.9.0
- Introduced-in: https://github.com/curl/curl/commit/623c3a8fa0bdb2751f1
libcurl is used by many applications, but not always advertised as such!
SOLUTION
------------
- Fixed-in: https://github.com/curl/curl/commit/3a537a4db9e65e545
RECOMMENDATIONS
---------------
We suggest you take one of the following actions immediately, in order of
preference:
A - Upgrade curl and libcurl to version 8.9.0
B - Apply the patch to your version and rebuild
C - Build your libcurl with an unaffected TLS backend
TIMELINE
---------
This issue was reported to the curl project on June 19, 2024. We contacted
distros@...nwall on July 15, 2024.
curl 8.9.0 was released on July 24 2024 around 06:00 UTC, coordinated with
the publication of this advisory.
CREDITS
-------
- Reported-by: z2_
- Patched-by: z2_
Thanks a lot!
--
/ daniel.haxx.se
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