CVE-2026-55991
MEDIUM
CVSS 5.9
CVE-2026-55991 — MEDIUM
Qu'est-ce que c'est ?
In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, a remote unauthenticated client can trigger a libngtcp2 assertion (if compiled with assertions on) and terminate the entire Unbound process using a single DNS-over-QUIC (DoQ) connection and one normal DNS query. This is caused by an erroneous error value passed to libngtcp2. When 'ngtcp2_conn_writev_stream()' returns 'NGTCP2_ERR_STREAM_DATA_BLOCKED', Unbound continues to call 'ngtcp2_ccerr_set_application_error()' with a '-1' error value. The 'int' literal '-1' is implicitly converted to the function's 'uint64_t error_code' parameter as '0xFFFFFFFFFFFFFFFF'. The follow-on 'ngtcp2_conn_write_connection_close()' serialises that value as a QUIC variable-length integer; because '2^64-1' exceeds the 62-bit varint ceiling, 'ngtcp2_put_uvarintlen()' fails 'assert(n < 4611686018427387904ULL)' and the whole resolver process aborts. A remote, unauthenticated DoQ client can trigger this deterministically with a single QUIC connection by advertising 'initial_max_stream_data_bidi_local = 1' in its transport parameters and sending one DoQ query without ever reading the stream.
Technologies affectées
Non précisé par la fiche NVD.
Recommandation
Vérifie la disponibilité d'un correctif pour la technologie concernée et applique-le dès que possible. Consulte la fiche NVD pour les références officielles du fournisseur.
Exploits publics connus (0)
Aucun proof-of-concept public trouvé sur GitHub à ce jour. Ça peut changer : les PoC sont souvent publiés plusieurs jours ou semaines après la divulgation.