Quick answers
- Is CVE-2026-75143 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-75143 being exploited in the wild.
- How severe is CVE-2026-75143?
- Critical severity, with a CVSS score of 9.8, published 19 August 2026.
- Which products and versions are affected?
- Ffmpeg before commit 1c10bcc.
- Is there a fix for CVE-2026-75143?
- A patch was published on 2026-08-04: Patch committed as 1c10bcc Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-75143 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-75143?
- Check whether you run Ffmpeg at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability is a heap buffer overflow in the librist_read() function within libavformat/librist.c. The vulnerable code ignored the caller-provided buffer size argument and instead copied the full received payload length into the destination buffer, causing an overflow when the payload exceeded the buffer capacity. This is triggered via the async:rist:// URL scheme, where the async wrapper supplies a smaller buffer than the received payload size. A remote RIST sender can exploit this by transmitting a packet with a payload larger than the caller's buffer, leading to out-of-bounds memory write. The fix clamps the memcpy() operation to the smaller of the payload length and caller-provided buffer size, respecting the URLProtocol.url_read contract.
Affected products
- FFmpeg FFmpeg before commit 1c10bcc
Timeline
- 2026-08-19: disclosed: CVE-2026-75143 published
- 2026-08-04: patched: Patch committed as 1c10bcc
- 2026-08-11: patched: Fix merged into FFmpeg master, targeted for FFmpeg 9.0 release