Description
FFmpeg through 9.0.2 contains an information disclosure vulnerability in flashsv_decode_block() in libavcodec/flashsv.c that copies uninitialized heap memory into decoded frames when inflate output is short. Attackers can supply a crafted FLV with an FSV1 stream whose zlib block data decompresses short, then recover heap contents from the decoded or re-encoded output.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| FFmpeg | FFmpeg | ≤ 9.0.2 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | ffmpeg | No fix yet | — |
Show 6 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 26.04 LTS | ffmpeg | No fix yet | — |
| Ubuntu Pro 24.04 LTS | ffmpeg | No fix yet | — |
| Ubuntu Pro 22.04 LTS | ffmpeg | No fix yet | — |
| Ubuntu Pro 20.04 LTS | ffmpeg | No fix yet | — |
| Ubuntu Pro 18.04 LTS | ffmpeg | No fix yet | — |
| Ubuntu Pro 16.04 LTS | ffmpeg | No fix yet | — |
Advisories 1
- WID-SEC-2026-4419 ffmpeg: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 9, 2026
References
- https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24464 issue-tracking
- Patch Commit patch
- Patch Commit patch
- https://github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/flashsv.c#L248 technical-description
- https://github.com/FFmpeg/FFmpeg product
- VulnCheck Advisory: FFmpeg through 9.0.2 Information Disclosure via Flash Screen Video Decoder third-party-advisory