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[SECURITY ADVISORY] curl: CVE-2024-6197: freeing stack buffer in utf8asn1str
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From: Daniel Stenberg via curl-users <curl-users_at_lists.haxx.se>
Date: Wed, 24 Jul 2024 08:34:35 +0200 (CEST)
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
Date: Wed, 24 Jul 2024 08:34:35 +0200 (CEST)
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_at_openwall 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 | Commercial curl support up to 24x7 is available! | Private help, bug fixes, support, ports, new features | https://curl.se/support.html -- Unsubscribe: https://lists.haxx.se/mailman/listinfo/curl-users Etiquette: https://curl.se/mail/etiquette.htmlReceived on 2024-07-24