FFmpeg through 9.0.2 APNG Encoder Heap Buffer Overflow via encode_apng()
Affects FFmpeg through 9.0.2 when the APNG encoder handles video whose frame size changes mid-stream. No vendor rating or fixed version is listed in the checked facts.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fix or patch referenced
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. Video frame size changes mid-stream while using the APNG encoder
- Last modified
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 12/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
FFmpeg through 9.0.2 contains a heap buffer overflow vulnerability in the APNG encoder's encode_apng() function in libavcodec/pngenc.c when frame size changes mid-stream. Attackers can supply crafted media whose resolution grows mid-stream, causing APNG_DISPOSE_OP_BACKGROUND memset writes past prev_frame and crashing or corrupting heap memory in transcoding applications.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure5/25Specific setups only
- Reach?/20Unknown. No tracked technology or package matched
- Severity7.3/10CVSS 7.3
- No patch0/5No signal
What would change the score
- Would score about 62 if added to CISA KEV
- Would score about 57 if CISA's SSVC rates exploitation active
- Would score about 22 if CISA's SSVC rates it automatable
What to do
Check whether your setup matches what the bug needs.
Video frame size changes mid-stream while using the APNG encoderApply the patch listed under Evidence.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- FFmpeg FFmpeg
through 9.0.2
Evidence 5
- Patch
- Report
- Repository
- Repository
- Link
Corrections
None so far.
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Questions about CVE-2026-125218
Is CVE-2026-125218 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
A bug in FFmpeg's APNG encoder (encode_apng) lets a memset write past the end of the prev_frame heap buffer when the frame size changes mid-stream. This can crash or corrupt heap memory in transcoding applications.Source: vulncheck.com
Which versions are affected by CVE-2026-125218?
FFmpeg: through 9.0.2.Source: cve.now feed data
Am I affected, and how do I check?
Versions from the start of the range through FFmpeg 9.0.2 are listed as affected. The bug needs the APNG encoder and a video whose frame size changes mid-stream; check the FFmpeg version with ffmpeg -version and whether APNG output is used in the encoding setup.Source: vulncheck.com
How do I fix CVE-2026-125218?
The checked facts do not list a fixed FFmpeg version. Check the FFmpeg project's release notes or the vendor advisory for a release that includes the fix, and upgrade to it once it is available.Source: vulncheck.com