FFmpeg through 9.0.2 Heap Buffer Overflow via DVB Subtitle Encoder
Affects FFmpeg through 9.0.2 when input with many bitmap subtitle rectangles is transcoded to the dvbsub encoder. CVSS rates it 8.5 (high); no vendor rating or fix is listed.
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. Input contains many bitmap subtitle rectangles and is transcoded to the dvbsub 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? →
- 14/100 · 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 dvbsub_encode() in libavcodec/dvbsubenc.c that undercounts each CLUT segment header by two bytes. Attackers can supply a file with many bitmap subtitle rectangles that, when transcoded to the dvbsub encoder, writes past the output buffer and corrupts heap memory.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure5/25Specific setups only
- Reach?/20Unknown. No tracked technology or package matched
- Severity8.5/10CVSS 8.5
- No patch0/5No signal
What would change the score
- Would score about 64 if added to CISA KEV
- Would score about 59 if CISA's SSVC rates exploitation active
- Would score about 24 if CISA's SSVC rates it automatable
What to do
Check whether your setup matches what the bug needs.
Input contains many bitmap subtitle rectangles and is transcoded to the dvbsub 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.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-125233
Is CVE-2026-125233 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?
Transcoding certain input to the DVB subtitle encoder writes past the output buffer and corrupts heap memory.Source: vulncheck.com
Which versions are affected by CVE-2026-125233?
FFmpeg: through 9.0.2.Source: cve.now feed data
Am I affected, and how do I check?
FFmpeg versions through 9.0.2 are listed as affected, with no earlier lower bound given. The triggering setup is input containing many bitmap subtitle rectangles that is transcoded to the dvbsub encoder; check your version with ffmpeg -version and whether dvbsub encoding is used.Source: vulncheck.com
How do I fix CVE-2026-125233?
The checked facts do not name a fixed version, so no upgrade target can be given. Check the FFmpeg project's advisory for a fixed release.Source: vulncheck.com