{"id":"CVE-2026-80819","state":"PUBLISHED","title":"Bluetooth: RFCOMM: take rfcomm_mutex for the deferred setup accept","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: RFCOMM: take rfcomm_mutex for the deferred setup accept\n\nrfcomm_sock_recvmsg() completes a deferred setup by calling\nrfcomm_dlc_accept() without holding any RFCOMM lock:\n\n\tif (test_and_clear_bit(RFCOMM_DEFER_SETUP, &d->flags)) {\n\t\trfcomm_dlc_accept(d);\n\t\treturn 0;\n\t}\n\nand rfcomm_dlc_accept() dereferences the session on its first line:\n\n\tstruct sock *sk = d->session->sock->sk;\n\nEvery other path that touches d->session runs under rfcomm_mutex:\nrfcomm_dlc_open(), rfcomm_dlc_close(), rfcomm_dlc_exists(),\nrfcomm_dlc_send_rpn(), and the RFCOMM thread through\nrfcomm_process_sessions(). rfcomm_connect_ind() is even documented as\n\"called under rfcomm_lock()\". This call site is the only one that skips\nit.\n\nThe RFCOMM_DEFER_SETUP bit looks like it serialises the accept against\nteardown, since __rfcomm_dlc_close() returns early when it wins the\ntest_and_clear. But rfcomm_recv_disc() forces the state first:\n\n\td->state = BT_CLOSED;\n\t__rfcomm_dlc_close(d, err);\n\nand the early return only covers BT_CONNECT, BT_CONFIG, BT_OPEN and\nBT_CONNECT2. With the state already BT_CLOSED that switch does not\nmatch, the bit is never consulted, and __rfcomm_dlc_close() falls\nthrough to rfcomm_dlc_unlink(), which sets d->session = NULL.\n\nSo a remote DISC on a deferred dlc clears the session while leaving\nRFCOMM_DEFER_SETUP set. The next recvmsg() then passes the\ntest_and_clear and dereferences a NULL session. No timing window is\nneeded: once the DISC has been processed, the dereference is\nunconditional.\n\nGive rfcomm_dlc_accept() the same shape as rfcomm_dlc_open() and\nrfcomm_dlc_close(): an exported wrapper that takes rfcomm_mutex and\nre-checks the session, around a __rfcomm_dlc_accept() that the two\nin-core callers, which already hold the mutex, keep using.\n\nReproduced on a KASAN + PROVE_LOCKING kernel with a BR/EDR peer emulated\nover /dev/vhci: the peer brings up an ACL link, opens L2CAP on the\nRFCOMM PSM, starts a session, opens a dlc on a channel bound with\nBT_DEFER_SETUP, and sends DISC after the socket is accepted. recv() on\nthe accepted socket then hits:\n\n  Oops: general protection fault\n  KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]\n  RIP: 0010:rfcomm_dlc_accept+0x54/0x350\n  Call Trace:\n    rfcomm_sock_recvmsg+0x1cd/0x230\n    sock_recvmsg+0x166/0x1c0\n    __sys_recvfrom+0x20d/0x300\n\n0x10 is the offset of sock in struct rfcomm_session. With this patch the\nsame run completes with recv() returning 0 and no report, and lockdep\nstays quiet, confirming rfcomm_mutex is still taken before lock_sock on\nthis path as it is on the thread side.","publishedAt":"2026-09-04T15:13:40.309Z","updatedAt":"2026-10-19T08:44:12.945Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"bb23c0ab824653be4aa7dfca15b07b3059717004","status":"affected","lessThan":"d8d686dd5662a7c4745e4515f1237a9f3b7df181","versionType":"git"},{"version":"bb23c0ab824653be4aa7dfca15b07b3059717004","status":"affected","lessThan":"eb71d5a1ea8ff2683e394b48ae3cd676037ab4c2","versionType":"git"},{"version":"bb23c0ab824653be4aa7dfca15b07b3059717004","status":"affected","lessThan":"56f0aa75c7640e46397ef73bea251fcbef9150c0","versionType":"git"},{"version":"bb23c0ab824653be4aa7dfca15b07b3059717004","status":"affected","lessThan":"362726c9c6e56eea4262109183e49868c39ccd3a","versionType":"git"},{"version":"bb23c0ab824653be4aa7dfca15b07b3059717004","status":"affected","lessThan":"825b95561d7b7c393df9e7bc295451aaeadc3d18","versionType":"git"},{"version":"bb23c0ab824653be4aa7dfca15b07b3059717004","status":"affected","lessThan":"d4b1a13b1eff2e80925c7368ffdeaaa50cba93df","versionType":"git"},{"version":"bb23c0ab824653be4aa7dfca15b07b3059717004","status":"affected","lessThan":"355bfd57ca4ca881c6eb03ca813b440a094b1f44","versionType":"git"},{"version":"bb23c0ab824653be4aa7dfca15b07b3059717004","status":"affected","lessThan":"b405c2f96ae2e37375105881890f7738833b1d62","versionType":"git"},{"version":"bb23c0ab824653be4aa7dfca15b07b3059717004","status":"affected","lessThan":"43a556b2fd43f2df6dded59c2e26560a27874c24","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bluetooth/rfcomm/core.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.30","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.30","versionType":"semver"},{"version":"5.10.267","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.218","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.185","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.154","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.106","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.47","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.11","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2.1","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bluetooth/rfcomm/core.c"]}],"references":["https://git.kernel.org/stable/c/d8d686dd5662a7c4745e4515f1237a9f3b7df181","https://git.kernel.org/stable/c/eb71d5a1ea8ff2683e394b48ae3cd676037ab4c2","https://git.kernel.org/stable/c/56f0aa75c7640e46397ef73bea251fcbef9150c0","https://git.kernel.org/stable/c/362726c9c6e56eea4262109183e49868c39ccd3a","https://git.kernel.org/stable/c/825b95561d7b7c393df9e7bc295451aaeadc3d18","https://git.kernel.org/stable/c/d4b1a13b1eff2e80925c7368ffdeaaa50cba93df","https://git.kernel.org/stable/c/355bfd57ca4ca881c6eb03ca813b440a094b1f44","https://git.kernel.org/stable/c/b405c2f96ae2e37375105881890f7738833b1d62","https://git.kernel.org/stable/c/43a556b2fd43f2df6dded59c2e26560a27874c24"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:07.220Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/80xxx/CVE-2026-80819.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-80819","state":"PUBLISHED","datePublished":"2026-09-04T15:13:40.309Z","dateUpdated":"2026-10-19T08:44:12.945Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-26T14:34:25.795Z"},"containers":{"cna":{"title":"Bluetooth: RFCOMM: take rfcomm_mutex for the deferred setup accept","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: RFCOMM: take rfcomm_mutex for the deferred setup accept\n\nrfcomm_sock_recvmsg() completes a deferred setup by calling\nrfcomm_dlc_accept() without holding any RFCOMM lock:\n\n\tif (test_and_clear_bit(RFCOMM_DEFER_SETUP, &d->flags)) {\n\t\trfcomm_dlc_accept(d);\n\t\treturn 0;\n\t}\n\nand rfcomm_dlc_accept() dereferences the session on its first line:\n\n\tstruct sock *sk = d->session->sock->sk;\n\nEvery other path that touches d->session runs under rfcomm_mutex:\nrfcomm_dlc_open(), rfcomm_dlc_close(), rfcomm_dlc_exists(),\nrfcomm_dlc_send_rpn(), and the RFCOMM thread through\nrfcomm_process_sessions(). rfcomm_connect_ind() is even documented as\n\"called under rfcomm_lock()\". This call site is the only one that skips\nit.\n\nThe RFCOMM_DEFER_SETUP bit looks like it serialises the accept against\nteardown, since __rfcomm_dlc_close() returns early when it wins the\ntest_and_clear. But rfcomm_recv_disc() forces the state first:\n\n\td->state = BT_CLOSED;\n\t__rfcomm_dlc_close(d, err);\n\nand the early return only covers BT_CONNECT, BT_CONFIG, BT_OPEN and\nBT_CONNECT2. With the state already BT_CLOSED that switch does not\nmatch, the bit is never consulted, and __rfcomm_dlc_close() falls\nthrough to rfcomm_dlc_unlink(), which sets d->session = NULL.\n\nSo a remote DISC on a deferred dlc clears the session while leaving\nRFCOMM_DEFER_SETUP set. The next recvmsg() then passes the\ntest_and_clear and dereferences a NULL session. No timing window is\nneeded: once the DISC has been processed, the dereference is\nunconditional.\n\nGive rfcomm_dlc_accept() the same shape as rfcomm_dlc_open() and\nrfcomm_dlc_close(): an exported wrapper that takes rfcomm_mutex and\nre-checks the session, around a __rfcomm_dlc_accept() that the two\nin-core callers, which already hold the mutex, keep using.\n\nReproduced on a KASAN + PROVE_LOCKING kernel with a BR/EDR peer emulated\nover /dev/vhci: the peer brings up an ACL link, opens L2CAP on the\nRFCOMM PSM, starts a session, opens a dlc on a channel bound with\nBT_DEFER_SETUP, and sends DISC after the socket is accepted. recv() on\nthe accepted socket then hits:\n\n  Oops: general protection fault\n  KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]\n  RIP: 0010:rfcomm_dlc_accept+0x54/0x350\n  Call Trace:\n    rfcomm_sock_recvmsg+0x1cd/0x230\n    sock_recvmsg+0x166/0x1c0\n    __sys_recvfrom+0x20d/0x300\n\n0x10 is the offset of sock in struct rfcomm_session. With this patch the\nsame run completes with recv() returning 0 and no report, and lockdep\nstays quiet, confirming rfcomm_mutex is still taken before lock_sock on\nthis path as it is on the thread side."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"bb23c0ab824653be4aa7dfca15b07b3059717004","status":"affected","lessThan":"d8d686dd5662a7c4745e4515f1237a9f3b7df181","versionType":"git"},{"version":"bb23c0ab824653be4aa7dfca15b07b3059717004","status":"affected","lessThan":"eb71d5a1ea8ff2683e394b48ae3cd676037ab4c2","versionType":"git"},{"version":"bb23c0ab824653be4aa7dfca15b07b3059717004","status":"affected","lessThan":"56f0aa75c7640e46397ef73bea251fcbef9150c0","versionType":"git"},{"version":"bb23c0ab824653be4aa7dfca15b07b3059717004","status":"affected","lessThan":"362726c9c6e56eea4262109183e49868c39ccd3a","versionType":"git"},{"version":"bb23c0ab824653be4aa7dfca15b07b3059717004","status":"affected","lessThan":"825b95561d7b7c393df9e7bc295451aaeadc3d18","versionType":"git"},{"version":"bb23c0ab824653be4aa7dfca15b07b3059717004","status":"affected","lessThan":"d4b1a13b1eff2e80925c7368ffdeaaa50cba93df","versionType":"git"},{"version":"bb23c0ab824653be4aa7dfca15b07b3059717004","status":"affected","lessThan":"355bfd57ca4ca881c6eb03ca813b440a094b1f44","versionType":"git"},{"version":"bb23c0ab824653be4aa7dfca15b07b3059717004","status":"affected","lessThan":"b405c2f96ae2e37375105881890f7738833b1d62","versionType":"git"},{"version":"bb23c0ab824653be4aa7dfca15b07b3059717004","status":"affected","lessThan":"43a556b2fd43f2df6dded59c2e26560a27874c24","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bluetooth/rfcomm/core.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.30","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.30","versionType":"semver"},{"version":"5.10.267","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.218","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.185","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.154","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.106","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.47","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.11","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2.1","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bluetooth/rfcomm/core.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/d8d686dd5662a7c4745e4515f1237a9f3b7df181"},{"url":"https://git.kernel.org/stable/c/eb71d5a1ea8ff2683e394b48ae3cd676037ab4c2"},{"url":"https://git.kernel.org/stable/c/56f0aa75c7640e46397ef73bea251fcbef9150c0"},{"url":"https://git.kernel.org/stable/c/362726c9c6e56eea4262109183e49868c39ccd3a"},{"url":"https://git.kernel.org/stable/c/825b95561d7b7c393df9e7bc295451aaeadc3d18"},{"url":"https://git.kernel.org/stable/c/d4b1a13b1eff2e80925c7368ffdeaaa50cba93df"},{"url":"https://git.kernel.org/stable/c/355bfd57ca4ca881c6eb03ca813b440a094b1f44"},{"url":"https://git.kernel.org/stable/c/b405c2f96ae2e37375105881890f7738833b1d62"},{"url":"https://git.kernel.org/stable/c/43a556b2fd43f2df6dded59c2e26560a27874c24"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T08:44:12.945Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.30","versionEndExcluding":"5.10.267"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.30","versionEndExcluding":"5.15.218"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.30","versionEndExcluding":"6.1.185"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.30","versionEndExcluding":"6.6.154"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.30","versionEndExcluding":"6.12.106"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.30","versionEndExcluding":"6.18.47"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.30","versionEndExcluding":"7.1.11"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.30","versionEndExcluding":"7.2.1"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.30","versionEndExcluding":"7.3"}]}]}],"x_generator":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