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CVE-2026-66038— FFmpeg LCL/ZLIB Video Decoder Information Disclosure via lcldec.c

Quick assessment

Affected
FFmpeg FFmpeg
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

FFmpeg是FFmpeg组织开源的一套可录制、转换以及流化音视频的完整解决方案。 FFmpeg 8.1.2及之前版本存在资源管理错误漏洞，该漏洞源于LCL/ZLIB视频解码器中的zlib_decomp()函数将短解压缩视为非致命并继续RGB24转换路径，导致未初始化堆内存内容被复制到攻击者可观察的AVFrame输出中，可能造成信息泄露并绕过ASLR。

CVSS 6.5 · Medium EPSS 0.44% · P36

Affected Version Matrix 2

VendorProduct Version RangeStatus
FFmpeg FFmpeg ≤ 8.1.2 affected
86708357d126af84c16f80d9c57335d1e8c845c5 unaffected
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I. Basic Information for CVE-2026-66038

Vulnerability Information
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Vulnerability Title
FFmpeg LCL/ZLIB Video Decoder Information Disclosure via lcldec.c
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对未经初始化资源的使用
Source: CVE Program / CVE List V5
Vulnerability Title
FFmpeg 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
FFmpeg是FFmpeg组织开源的一套可录制、转换以及流化音视频的完整解决方案。 FFmpeg 8.1.2及之前版本存在资源管理错误漏洞，该漏洞源于LCL/ZLIB视频解码器中的zlib_decomp()函数将短解压缩视为非致命并继续RGB24转换路径，导致未初始化堆内存内容被复制到攻击者可观察的AVFrame输出中，可能造成信息泄露并绕过ASLR。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
FFmpeg FFmpeg 0 ~ 8.1.2 -

II. Public POCs for CVE-2026-66038

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III. Intelligence Information for CVE-2026-66038

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Patches & Fixes for CVE-2026-66038 (2)

Vendor Advisories for CVE-2026-66038 (1)

Same Patch Batch · FFmpeg · 2026-07-24 · 6 CVEs total

CVE-2026-66036 8.8 HIGH FFmpeg Heap Out-of-Bounds Write in vf_hqdn3d Filter
CVE-2026-66040 8.8 HIGH FFmpeg Heap Out-of-Bounds Write via PNG/APNG eXIf Encoder
CVE-2026-66041 8.8 HIGH FFmpeg 7.0 - 8.1.2 Heap Out-of-Bounds Write via vf_quirc Filter
CVE-2026-66039 8.8 HIGH FFmpeg MACE6 Audio Decoder Heap Out-of-Bounds Write via CAF File
CVE-2026-66037 6.5 MEDIUM FFmpeg IAMF Demuxer Uncontrolled Resource Consumption via mix_presentation_obu()

IV. Related Vulnerabilities

Same product: FFmpeg
Same vendor: FFmpeg
Same weakness: CWE-908

V. Comments for CVE-2026-66038

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