CVE details
CVE-2026-66038
FFmpeg through 8.1.2, fixed in commit 8670835, contains an information disclosure vulnerability in the LCL/ZLIB video decoder that allows attackers to expose uninitialized heap memory by supplying a valid zlib stream that inflates to fewer bytes than the expected frame size. The zlib_decomp() function in lcldec.c treats short decompression as non-fatal and continues to the RGB24 conversion path, which copies a full frame's worth of rows from the allocation buffer using original frame dimensions, causing uninitialized heap contents including pointer-derived allocator bytes to be copied into the attacker-observable AVFrame output and potentially defeating ASLR in long-lived media processing services.
Affected ports (3)
| Port | Package | Version | Status | Maintainer |
|---|---|---|---|---|
| multimedia/ffmpeg3 | ffmpeg3 | 3.0.2_1 | unaddressed | kreinholz@gmail.com |
| multimedia/linux-rl9-ffmpeg | linux-rl9-ffmpeg-libs | 7.1.5 | unaddressed | emulation@FreeBSD.org |
| multimedia/ffmpeg4 | ffmpeg4 | 4.4.8_2 | possibly backported | monwarez@mailoo.org |
Template for a VuXML entry
Range taken from the CVE record, check it before committing. make newentry in security/vuxml creates the vid.
<vuln vid="FIXME (make newentry)">
<topic>FIXME -- FIXME</topic>
<affects>
<package>
<name>ffmpeg3</name>
<range><lt>FIXME</lt></range>
</package>
<package>
<name>linux-rl9-ffmpeg-libs</name>
<range><lt>FIXME</lt></range>
</package>
</affects>
<description>
<body xmlns="http://www.w3.org/1999/xhtml">
<p>FFmpeg through 8.1.2, fixed in commit 8670835, contains an information
disclosure vulnerability in the LCL/ZLIB video decoder that allows
attackers to expose uninitialized heap memory by supplying a valid
zlib stream that inflates to fewer bytes than the expected frame size.
The zlib_decomp() function in lcldec.c treats short decompression as
non-fatal and continues to the RGB24 conversion path, which copies a
full frame's worth of rows from the allocation buffer using original
frame dimensions, causing uninitialized heap contents including
pointer-derived allocator bytes to be copied into the
attacker-observable AVFrame output and potentially defeating ASLR in
long-lived media processing services.</p>
</body>
</description>
<references>
<cvename>CVE-2026-66038</cvename>
<url>https://nvd.nist.gov/vuln/detail/CVE-2026-66038</url>
</references>
<dates>
<discovery>2026-07-24</discovery>
<entry>2026-10-25</entry>
</dates>
</vuln>