Use-after-free in connection ID iterator and FFI functions

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.