# CVE-2026-95121: mp4v2 integer underflow in RTP atom parsing

Source: https://junglewise.ai/threats/cve-2026-95121-an-issue-in-mp4v2-2-0-0-allows-an-attacker-to-execute-arbitrary  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-13. Updated: 2026-10-16  
License: CC BY 4.0 with a link back

CVE-2026-95121 · Severity: high · CVSS 7.8 · Published 2026-10-13

mp4v2 is a library for reading and writing MP4 video files. A flaw in how it parses specially crafted MP4 files can cause it to attempt allocating an enormous amount of memory (near 2 trillion bytes), leading to a denial-of-service crash when processing a malicious file. An attacker can trigger this by sending a crafted MP4 file to an application using mp4v2.

Technologies: [TechSmith Mp4v2](https://junglewise.ai/threats/technologies/mp4v2). Vendors: [TechSmith](https://junglewise.ai/threats/vendors/techsmith).

## Quick answers

**Is CVE-2026-95121 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-95121 being exploited in the wild.

**How severe is CVE-2026-95121?** High severity, with a CVSS score of 7.8, published 13 October 2026.

**Which products and versions are affected?** TechSmith Mp4v2 2.0.0.

**Is there a fix for CVE-2026-95121?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-95121 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-95121?** Check whether you run TechSmith Mp4v2 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

An integer underflow in MP4RtpAtom::ReadHntiType() occurs when parsing an undersized rtp atom within an hnti container. The vulnerable code computes size as GetEnd() - m_File.GetPosition() without bounds checking; if the atom is too small, this subtraction underflows to a near-2^64 value, which is passed directly to MP4Malloc(). This triggers an excessive memory allocation attempt (CWE-191, CWE-789), causing denial of service.

## Affected products

- TechSmith mp4v2 2.0.0

## Timeline

- 2026-10-13: disclosed
- 2026-10-10: other: Advisory published on GitHub

## References

- [https://gist.github.com/1820893135-pixel/c56b6a1627453e67ca2fb7e29bae95c6](https://gist.github.com/1820893135-pixel/c56b6a1627453e67ca2fb7e29bae95c6)
- [https://github.com/TechSmith/mp4v2/issues/98](https://github.com/TechSmith/mp4v2/issues/98)

## Related threats

- [mp4v2 NULL pointer dereference in GenerateTracks](https://junglewise.ai/threats/cve-2026-95122-mp4v2-2-0-0-contains-a-null-pointer-dereference-vulnerability-in)