CVE-2026-91096: facebook proxygen Use After Free

Vulnerability summary

CVE-2026-91096 is a high (CVSS 7.5) Use After Free vulnerability in facebook proxygen. EPSS estimates a 0.26% chance of exploitation in the next 30 days, higher than 16% of scored vulnerabilities.

Timeline

1. 28-09-2026
   PublishedVulnerability first disclosed.
2. 30-09-2026
   Last modifiedVulnerability information updated.

Description

In proxygen from v2024.10.28.00 until v2026.09.28.00, WebTransportImpl::terminateSessionStreams (WebTransportImpl::destroy in releases before v2025.08.18.00) failed to unregister read callbacks for streams that were no longer open before destroying them. The transport could then invoke a read callback that had been freed.

• 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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.