CVE-2026-84895: facebook proxygen Use After Free

Vulnerability summary

CVE-2026-84895 is a high (CVSS 7.3) Use After Free vulnerability in facebook proxygen. EPSS estimates a 0.19% chance of exploitation in the next 30 days, higher than 8.6% of scored vulnerabilities.

Timeline

1. 28-09-2026
   PublishedVulnerability first disclosed.
2. 01-10-2026
   Last modifiedVulnerability information updated.

Description

In proxygen from v2026.04.06.00 until v2026.09.28.00, QuicWtSession::closeSession accesses its member fields after calling the base QuicWtSessionBase::closeSession method. The base method notifies the session handler, which may release the last reference to the session and destroy it.

• CWE-416Use After FreeThe product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.