CVE-2026-52296: FFmpeg WMA Buffer Overflow Vulnerability

CVE-2026-52296 Overview

CVE-2026-52296 is an out-of-bounds read vulnerability [CWE-125] in FFmpeg versions prior to 9.0. The flaw resides in libavcodec/wmaenc.c, where the Windows Media Audio (WMA) encoder allocates extradata buffers without the padding required by FFmpeg's buffer contracts. Downstream code that assumes the presence of AV_INPUT_BUFFER_PADDING_SIZE bytes can read past the allocated region. Exploitation requires local access and specific input conditions, limiting real-world impact to availability.

Critical Impact
A local attacker supplying crafted WMA encoding inputs can trigger an out-of-bounds read that may crash the FFmpeg process, resulting in denial of service.

Affected Products

FFmpeg versions prior to 9.0
libavcodec component (wmaenc.c)
Applications and pipelines that link against vulnerable FFmpeg builds for WMA encoding

Discovery Timeline

2026-09-13 - CVE-2026-52296 published to the National Vulnerability Database
2026-09-15 - Last updated in NVD database

Technical Details for CVE-2026-52296

Vulnerability Analysis

The vulnerability affects the WMA encoder in libavcodec/wmaenc.c. FFmpeg requires that certain buffers, including codec extradata, be allocated with trailing padding bytes defined by AV_INPUT_BUFFER_PADDING_SIZE. This padding permits optimized readers, including SIMD and bitstream routines, to read slightly past the logical end of the buffer without touching unmapped memory.

The WMA encoder allocation paths omitted this required padding when producing extradata. Consumers of the extradata subsequently perform reads that extend beyond the allocated region, producing an out-of-bounds read condition. The upstream fix in commit 23227a444d corrects the allocation size in the affected paths.

Root Cause

The root cause is a missing size adjustment during extradata buffer allocation. The allocator sized the buffer to the exact payload length rather than payload length plus AV_INPUT_BUFFER_PADDING_SIZE. Any downstream routine relying on the padding contract can then read uninitialized or unrelated adjacent memory.

Attack Vector

Exploitation requires local access and depends on specific encoder inputs, reflecting the high attack complexity. An attacker who can invoke FFmpeg's WMA encoder against controlled inputs may trigger the out-of-bounds read. The most likely outcome is a process crash or transient information exposure to adjacent memory. There is no evidence of confidentiality or integrity impact based on the available scoring vector. No public exploit or CISA KEV listing is associated with this issue.

No verified proof-of-concept code is published. Technical details are documented in FFmpeg Pull Request #22988, the upstream commit 23227a444d, and the Kenan Kamel Vulnerabilities Reference.

Detection Methods for CVE-2026-52296

Indicators of Compromise

Unexpected crashes or segmentation faults in processes invoking FFmpeg WMA encoding routines
AddressSanitizer or Valgrind reports flagging heap-buffer-overflow reads inside libavcodec extradata handlers
Repeated failed transcoding jobs against WMA outputs on media processing servers

Detection Strategies

Inventory installed FFmpeg binaries and shared libraries across servers and workstations, flagging versions earlier than 9.0
Run software composition analysis against build manifests and container images to identify embedded FFmpeg builds
Enable core dump collection on media processing hosts and inspect stack traces for frames within wmaenc.c

Monitoring Recommendations

Monitor telemetry from media conversion services for abnormal process termination rates
Alert on repeated invocation of FFmpeg with attacker-controllable arguments in shared or multi-tenant environments
Track file integrity of the FFmpeg installation to detect unauthorized version changes or downgrades

How to Mitigate CVE-2026-52296

Immediate Actions Required

Upgrade FFmpeg to version 9.0 or later on all affected systems
Rebuild and redistribute any applications, containers, or media pipelines that statically link against libavcodec
Restrict local execution of FFmpeg on shared hosts to trusted users and service accounts

Patch Information

The upstream fix is applied in FFmpeg commit 23227a444d, referenced in FFmpeg Pull Request #22988. The patch adjusts extradata allocation in libavcodec/wmaenc.c to include the required AV_INPUT_BUFFER_PADDING_SIZE bytes. Distribution maintainers should backport the change to supported FFmpeg branches. Verify the applied fix by reviewing the upstream commit 23227a444d.

Workarounds

Disable WMA encoding paths in FFmpeg builds where the codec is not required by configuring builds with --disable-encoder=wmav1 --disable-encoder=wmav2
Sandbox FFmpeg processes with seccomp, AppArmor, or SELinux profiles to contain the impact of crashes
Validate and constrain untrusted encoder inputs at ingest to reduce exposure to malformed processing jobs

bash

# Configuration example: verify installed FFmpeg version and rebuild without WMA encoders if unused
ffmpeg -version | head -n 1
./configure --disable-encoder=wmav1 --disable-encoder=wmav2
make && sudo make install