Facebook mvfst 2025.07.07.00 QUIC Server allocation of resources

Summaryinfo

A vulnerability identified as problematic has been detected in Facebook mvfst. The impacted element is an unknown function of the component QUIC Server. This manipulation causes allocation of resources. This vulnerability is handled as CVE-2026-119236. The attack can be initiated remotely. There is not any exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in Facebook mvfst. Affected by this vulnerability is some unknown functionality of the component QUIC Server. The manipulation with an unknown input leads to a allocation of resources vulnerability. The CWE definition for the vulnerability is CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. As an impact it is known to affect availability. The summary by CVE is:

An mvfst QUIC server retained CRYPTO frame data received at an encryption level (Initial or Handshake) that the TLS handshake had already moved past. Because the transport treated this data as delivered, it did not count against the CRYPTO stream buffer limit. A remote, unauthenticated client could complete a handshake, withhold its acknowledgment of the server's HANDSHAKE_DONE frame so that Handshake keys stay in use, and keep sending Handshake-level CRYPTO data at increasing offsets, causing unbounded memory growth on the server and leading to denial of service. This issue affects mvfst versions prior to v2026.11.09.00.

It is possible to read the advisory at facebook.com. This vulnerability is known as CVE-2026-119236 since 10/29/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 11/11/2026). The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

Upgrading to version 2026.11.09.00 eliminates this vulnerability.

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Productinfo

Type

• Social Network Software

Vendor

• Facebook

Name

• mvfst

Version

• 2025.07.07.00

License

• free

CPE 2.3info

• 🔒

CPE 2.2info

• 🔒

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