FFmpeg through 8.1.2, fixed in commit 8670835, contains an information disclosure vulnerability in the LCL/ZLIB video decoder that allows attackers… (CVE-2026-66038)
FFmpeg versions through 8.1.2 contain an information disclosure vulnerability in the LCL/ZLIB video decoder. This flaw allows attackers to expose uninitialized heap memory by providing a valid zlib stream that decompresses to fewer bytes than the expected frame size. The vulnerability arises because the decompression function treats short decompression as non-fatal and proceeds to copy a full frame's worth of data from the allocation buffer, potentially leaking sensitive memory contents. This may aid attackers in bypassing address space layout randomization (ASLR) in long-running media processing services.
AI Analysis
Technical Summary
An information disclosure vulnerability exists in FFmpeg through version 8.1.2 in the LCL/ZLIB video decoder. The zlib_decomp() function in lcldec.c does not properly handle cases where decompression results in fewer bytes than expected. It continues processing and copies a full frame's worth of rows from the allocation buffer, which includes uninitialized heap memory. This memory exposure can reveal pointer-derived allocator bytes, potentially assisting attackers in defeating ASLR protections in media processing environments. The issue was fixed in commit 8670835.
Potential Impact
Attackers can supply specially crafted zlib streams that cause the decoder to leak uninitialized heap memory contents in the output frame. This information disclosure may facilitate further attacks such as bypassing ASLR in long-lived media processing services using FFmpeg. No direct code execution or denial of service is described.
Mitigation Recommendations
A fix for this vulnerability is available in FFmpeg as of commit 8670835. Users should upgrade to a version including this commit to remediate the issue. Since the vulnerability affects FFmpeg software and is not a cloud service, remediation requires applying the official patch or updating FFmpeg to a fixed version. Patch status is confirmed by the vendor commit reference.
FFmpeg through 8.1.2, fixed in commit 8670835, contains an information disclosure vulnerability in the LCL/ZLIB video decoder that allows attackers… (CVE-2026-66038)
Description
FFmpeg versions through 8.1.2 contain an information disclosure vulnerability in the LCL/ZLIB video decoder. This flaw allows attackers to expose uninitialized heap memory by providing a valid zlib stream that decompresses to fewer bytes than the expected frame size. The vulnerability arises because the decompression function treats short decompression as non-fatal and proceeds to copy a full frame's worth of data from the allocation buffer, potentially leaking sensitive memory contents. This may aid attackers in bypassing address space layout randomization (ASLR) in long-running media processing services.
CVSS v4.0
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
An information disclosure vulnerability exists in FFmpeg through version 8.1.2 in the LCL/ZLIB video decoder. The zlib_decomp() function in lcldec.c does not properly handle cases where decompression results in fewer bytes than expected. It continues processing and copies a full frame's worth of rows from the allocation buffer, which includes uninitialized heap memory. This memory exposure can reveal pointer-derived allocator bytes, potentially assisting attackers in defeating ASLR protections in media processing environments. The issue was fixed in commit 8670835.
Potential Impact
Attackers can supply specially crafted zlib streams that cause the decoder to leak uninitialized heap memory contents in the output frame. This information disclosure may facilitate further attacks such as bypassing ASLR in long-lived media processing services using FFmpeg. No direct code execution or denial of service is described.
Mitigation Recommendations
A fix for this vulnerability is available in FFmpeg as of commit 8670835. Users should upgrade to a version including this commit to remediate the issue. Since the vulnerability affects FFmpeg software and is not a cloud service, remediation requires applying the official patch or updating FFmpeg to a fixed version. Patch status is confirmed by the vendor commit reference.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-8mx4-8xfc-qr43
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-66038"]
- Ecosystems
- []
- Database Specific Severity
- HIGH
- Cvss Version
- 4.0
Threat ID: 6a6542289c2644c7f808a023
Added to database: 07/25/2026, 23:09:28 UTC
Last enriched: 07/25/2026, 23:54:36 UTC
Last updated: 07/26/2026, 04:52:50 UTC
Views: 6
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