CVE-2026-65704: ffmpeg Integer Underflow (Wrap or Wraparound)

Vulnerability summary

CVE-2026-65704 is a high (CVSS 7.8) Integer Underflow (Wrap or Wraparound) vulnerability in ffmpeg. EPSS estimates a 0.18% chance of exploitation in the next 30 days, higher than 6.9% of scored vulnerabilities.

Timeline

1. 23-07-2026
   PublishedVulnerability first disclosed.
2. 28-07-2026
   Last modifiedVulnerability information updated.

Description

FFmpeg through 8.1.2 contains an out-of-bounds write vulnerability that allows attackers to cause heap corruption by supplying a crafted ffconcat file processed with the -safe 0 flag. The TY demuxer's demux_audio() function decrements packet size without bounds checking, producing a negative size value that is passed to memcpy() in shorten_decode_frame(), where conversion to size_t wraps the value to near SIZE_MAX and triggers reads beyond the source allocation and writes far beyond the Shorten decoder's bitstream buffer.

• CWE-191Integer Underflow (Wrap or Wraparound)The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.
• CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.