CVE-2026-11941: Use-after-free in connection ID iterator and FFI functions
Impact
Cloudflare Quiche was affected by 2 use-after-free vulnerabilities in the connection ID iterator FFI functions.
The quicheconnectioniditernext and quicheconnretiredscidnext functions would return a pointer to a ConnectionId to the applications via function arguments, but the 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.
quiche 0.29.2 is the earliest version containing the fix for this issue.
Other sources
Cloudflare Quiche was affected by 2 use-after-free vulnerabilities in the connection ID iterator FFI functions.
The “quicheconnectioniditernext” and “quicheconnretiredscidnext” 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.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
rust/quicheto a version that resolves this vulnerability.Fixed in 0.29.2 - Configuration
Ensure quiche is built without enabling the FFI API build-time feature flag (the FFI API is disabled by default).
rust/quiche FFI API build-time feature flag = disabled - Compensating control
Do not call the FFI functions quiche_connection_id_iter_next and quiche_conn_retired_scid_next in application code until quiche has been upgraded to 0.29.2.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-11941?
CVE-2026-11941 has a severity rating of medium with a score of 5.6.
What type of vulnerability is described in CVE-2026-11941?
CVE-2026-11941 describes a use-after-free vulnerability in the connection ID iterator and FFI functions in Cloudflare Quiche.
How do I fix CVE-2026-11941?
To fix CVE-2026-11941, update to the latest version of Cloudflare Quiche where the vulnerability has been addressed.
Which functions are affected by CVE-2026-11941?
CVE-2026-11941 affects the 'quiche_connection_id_iter_next' and 'quiche_conn_retired_scid_next' functions.
What are the potential impacts of CVE-2026-11941?
CVE-2026-11941 could lead to application crashes or unintended information exposure due to a use-after-free condition.