CVE-2026-11941: cloudflare quiche Use After Free

Vulnerability summary

CVE-2026-11941 is a medium (CVSS 5.6) Use After Free vulnerability in cloudflare quiche. EPSS estimates a 0.25% chance of exploitation in the next 30 days, higher than 15.4% of scored vulnerabilities.

Timeline

1. 19-06-2026
   PublishedVulnerability first disclosed.
2. 22-06-2026
   Last modifiedVulnerability information updated.

Description

Cloudflare Quiche was affected by 2 use-after-free vulnerabilities in the connection ID iterator FFI functions. The “quiche_connection_id_iter_next” and “quiche_conn_retired_scid_next” functions would return a pointer to a “ConnectionId” to the applications via function arguments, but the owned “ConnectionId” would be dropped at the end of those functions' scope. Only applications using those FFI functions are affected. The FFI API is disabled by default by a build-time feature flag. Impact If unpatched, an application calling the affected FFI functions will dereference freed memory. The most likely outcome is undefined behavior leading to a process crash (denial of service). Depending on allocator state, the read may also return adjacent heap contents, resulting in limited information disclosure or incorrect connection identifier handling. Mitigation Users are requested to upgrade to quiche 0.29.2 which is the earliest version containing the fix for this issue.

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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.