CVE-2026-80819

CVE CVE-2026-80819EUVD EUVD-2026-71254Veröffentlicht 2026-09-04T15:13:40.000Z

Was das Advisory beschreibt

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: RFCOMM: take rfcomm_mutex for the deferred setup accept rfcomm_sock_recvmsg() completes a deferred setup by calling rfcomm_dlc_accept() without holding any RFCOMM lock: if (test_and_clear_bit(RFCOMM_DEFER_SETUP, &d->flags)) { rfcomm_dlc_accept(d); return 0; } and rfcomm_dlc_accept() dereferences the session on its first line: struct sock *sk = d->session->sock->sk; Every other path that touches d->session runs under rfcomm_mutex: rfcomm_dlc_open(), rfcomm_dlc_close(), rfcomm_dlc_exists(), rfcomm_dlc_send_rpn(), and the RFCOMM thread through rfcomm_process_sessions(). rfcomm_connect_ind() is even documented as "called under rfcomm_lock()". This call site is the only one that skips it. The RFCOMM_DEFER_SETUP bit looks like it serialises the accept against teardown, since __rfcomm_dlc_close() returns early when it wins the test_and_clear. But rfcomm_recv_disc() forces the state first: d->state = BT_CLOSED; __rfcomm_dlc_close(d, err); and the early return only covers BT_CONNECT, BT_CONFIG, BT_OPEN and BT_CONNECT2. With the state already BT_CLOSED that switch does not match, the bit is never consulted, and __rfcomm_dlc_close() falls through to rfcomm_dlc_unlink(), which sets d->session = NULL. So a remote DISC on a deferred dlc clears the session while leaving RFCOMM_DEFER_SETUP set. The next recvmsg() then passes the test_and_clear and dereferences a NULL session. No timing window is needed: once the DISC has been processed, the dereference is unconditional. Give rfcomm_dlc_accept() the same shape as rfcomm_dlc_open() and rfcomm_dlc_close(): an exported wrapper that takes rfcomm_mutex and re-checks the session, around a __rfcomm_dlc_accept() that the two in-core callers, which already hold the mutex, keep using. Reproduced on a KASAN + PROVE_LOCKING kernel with a BR/EDR peer emulated over /dev/vhci: the peer brings up an ACL link, opens L2CAP on the RFCOMM PSM, starts a session, opens a dlc on a channel bound with BT_DEFER_SETUP, and sends DISC after the socket is accepted. recv() on the accepted socket then hits: Oops: general protection fault KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] RIP: 0010:rfcomm_dlc_accept+0x54/0x350 Call Trace: rfcomm_sock_recvmsg+0x1cd/0x230 sock_recvmsg+0x166/0x1c0 __sys_recvfrom+0x20d/0x300 0x10 is the offset of sock in struct rfcomm_session. With this patch the same run completes with recv() returning 0 and no report, and lockdep stays quiet, confirming rfcomm_mutex is still taken before lock_sock on this path as it is on the thread side.

Quelle: EUVD (ENISA), im Wortlaut der Meldung.

Produkte, die das Advisory nennt

Diese Angaben stammen aus der Meldung selbst, nicht aus einer Prüfung durch uns.

• Linux — Linux bb23c0ab824653be4aa7dfca15b07b3059717004 <d4b1a13b1eff2e80925c7368ffdeaaa50cba93df; patch: 6.18.47; 2.6.30; bb23c0ab824653be4aa7dfca15b07b3059717004 <43a556b2fd43f2df6dded59c2e26560a27874c24; bb23c0ab824653be4aa7dfca15b07b3059717004 <362726c9c6e56eea4262109183e49868c39ccd3a; patch: 7.3-rc1; patch: 6.12.106; patch: 7.1.11; bb23c0ab824653be4aa7dfca15b07b3059717004 <d8d686dd5662a7c4745e4515f1237a9f3b7df181; patch: 5.10.267; patch: 6.6.154; bb23c0ab824653be4aa7dfca15b07b3059717004 <355bfd57ca4ca881c6eb03ca813b440a094b1f44; bb23c0ab824653be4aa7dfca15b07b3059717004 <eb71d5a1ea8ff2683e394b48ae3cd676037ab4c2; patch: 0; patch: 5.15.218; patch: 7.2.1; bb23c0ab824653be4aa7dfca15b07b3059717004 <56f0aa75c7640e46397ef73bea251fcbef9150c0; bb23c0ab824653be4aa7dfca15b07b3059717004 <b405c2f96ae2e37375105881890f7738833b1d62; patch: 6.1.185; bb23c0ab824653be4aa7dfca15b07b3059717004 <825b95561d7b7c393df9e7bc295451aaeadc3d18

Die genannten Versionen sind die Angabe der Meldung. Patchlage vergleicht keine Versionsnummern und leitet aus ihnen keine Aussage ab — welche Version installiert ist, muss ein Mensch nachsehen.

Im Produktkatalog geführt

Für diese Produkte kann ein Bestand in Patchlage erfasst werden. Ein Advisory dazu erscheint am Morgen danach im Lagebericht.

• Linux — Linux

Patchlage meldet Treffer und Verdachtsfälle. Zu allem anderen sagt dieses System nichts — weder diese Seite noch der Lagebericht behauptet je, dass ein Bestand sicher ist.