{"id":"CVE-2026-23461","state":"PUBLISHED","title":"Bluetooth: L2CAP: Fix use-after-free in l2cap_unregister_user","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: L2CAP: Fix use-after-free in l2cap_unregister_user\n\nAfter commit ab4eedb790ca (\"Bluetooth: L2CAP: Fix corrupted list in\nhci_chan_del\"), l2cap_conn_del() uses conn->lock to protect access to\nconn->users. However, l2cap_register_user() and l2cap_unregister_user()\ndon't use conn->lock, creating a race condition where these functions can\naccess conn->users and conn->hchan concurrently with l2cap_conn_del().\n\nThis can lead to use-after-free and list corruption bugs, as reported\nby syzbot.\n\nFix this by changing l2cap_register_user() and l2cap_unregister_user()\nto use conn->lock instead of hci_dev_lock(), ensuring consistent locking\nfor the l2cap_conn structure.","publishedAt":"2026-04-03T15:15:41.051Z","updatedAt":"2026-10-19T18:35:45.372Z","severity":{"score":8.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"efc30877bd4bc85fefe98d80af60fafc86e5775e","status":"affected","lessThan":"11a87dd5df428a4b79a84d2790cac7f3c73f1f0d","versionType":"git"},{"version":"f87271d21dd4ee83857ca11b94e7b4952749bbae","status":"affected","lessThan":"c22a5e659959eb77c2fbb58a5adfaf3c3dab7abf","versionType":"git"},{"version":"ab4eedb790cae44313759b50fe47da285e2519d5","status":"affected","lessThan":"da3000cbe4851458a22be38bb18c0689c39fdd5f","versionType":"git"},{"version":"ab4eedb790cae44313759b50fe47da285e2519d5","status":"affected","lessThan":"71030f3b3015a412133a805ff47970cdcf30c2b8","versionType":"git"},{"version":"ab4eedb790cae44313759b50fe47da285e2519d5","status":"affected","lessThan":"752a6c9596dd25efd6978a73ff21f3b592668f4a","versionType":"git"},{"version":"18ab6b6078fa8191ca30a3065d57bf35d5635761","status":"affected","versionType":"git"},{"version":"6.6.84","status":"affected","lessThan":"6.6.130","versionType":"semver"},{"version":"6.12.20","status":"affected","lessThan":"6.12.78","versionType":"semver"},{"version":"6.13.8","status":"affected","lessThan":"6.14","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bluetooth/l2cap_core.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.14","versionType":"semver"},{"version":"6.6.130","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.78","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.20","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.10","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bluetooth/l2cap_core.c"]}],"references":["https://git.kernel.org/stable/c/11a87dd5df428a4b79a84d2790cac7f3c73f1f0d","https://git.kernel.org/stable/c/c22a5e659959eb77c2fbb58a5adfaf3c3dab7abf","https://git.kernel.org/stable/c/da3000cbe4851458a22be38bb18c0689c39fdd5f","https://git.kernel.org/stable/c/71030f3b3015a412133a805ff47970cdcf30c2b8","https://git.kernel.org/stable/c/752a6c9596dd25efd6978a73ff21f3b592668f4a"],"weaknesses":["CWE-362"],"ingestedAt":"2026-10-29T20:11:21.040Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/23xxx/CVE-2026-23461.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-23461","state":"PUBLISHED","datePublished":"2026-04-03T15:15:41.051Z","dateUpdated":"2026-10-19T18:35:45.372Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-01-13T15:37:46.021Z"},"containers":{"cna":{"title":"Bluetooth: L2CAP: Fix use-after-free in l2cap_unregister_user","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: L2CAP: Fix use-after-free in l2cap_unregister_user\n\nAfter commit ab4eedb790ca (\"Bluetooth: L2CAP: Fix corrupted list in\nhci_chan_del\"), l2cap_conn_del() uses conn->lock to protect access to\nconn->users. However, l2cap_register_user() and l2cap_unregister_user()\ndon't use conn->lock, creating a race condition where these functions can\naccess conn->users and conn->hchan concurrently with l2cap_conn_del().\n\nThis can lead to use-after-free and list corruption bugs, as reported\nby syzbot.\n\nFix this by changing l2cap_register_user() and l2cap_unregister_user()\nto use conn->lock instead of hci_dev_lock(), ensuring consistent locking\nfor the l2cap_conn structure."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"efc30877bd4bc85fefe98d80af60fafc86e5775e","status":"affected","lessThan":"11a87dd5df428a4b79a84d2790cac7f3c73f1f0d","versionType":"git"},{"version":"f87271d21dd4ee83857ca11b94e7b4952749bbae","status":"affected","lessThan":"c22a5e659959eb77c2fbb58a5adfaf3c3dab7abf","versionType":"git"},{"version":"ab4eedb790cae44313759b50fe47da285e2519d5","status":"affected","lessThan":"da3000cbe4851458a22be38bb18c0689c39fdd5f","versionType":"git"},{"version":"ab4eedb790cae44313759b50fe47da285e2519d5","status":"affected","lessThan":"71030f3b3015a412133a805ff47970cdcf30c2b8","versionType":"git"},{"version":"ab4eedb790cae44313759b50fe47da285e2519d5","status":"affected","lessThan":"752a6c9596dd25efd6978a73ff21f3b592668f4a","versionType":"git"},{"version":"18ab6b6078fa8191ca30a3065d57bf35d5635761","status":"affected","versionType":"git"},{"version":"6.6.84","status":"affected","lessThan":"6.6.130","versionType":"semver"},{"version":"6.12.20","status":"affected","lessThan":"6.12.78","versionType":"semver"},{"version":"6.13.8","status":"affected","lessThan":"6.14","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bluetooth/l2cap_core.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.14","versionType":"semver"},{"version":"6.6.130","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.78","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.20","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.10","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bluetooth/l2cap_core.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/11a87dd5df428a4b79a84d2790cac7f3c73f1f0d"},{"url":"https://git.kernel.org/stable/c/c22a5e659959eb77c2fbb58a5adfaf3c3dab7abf"},{"url":"https://git.kernel.org/stable/c/da3000cbe4851458a22be38bb18c0689c39fdd5f"},{"url":"https://git.kernel.org/stable/c/71030f3b3015a412133a805ff47970cdcf30c2b8"},{"url":"https://git.kernel.org/stable/c/752a6c9596dd25efd6978a73ff21f3b592668f4a"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":8.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:A - The vulnerable L2CAP/HIDP teardown path is reachable through Bluetooth ACL/L2CAP connection handling by a nearby Bluetooth peer. Bluetooth proximity is an adjacent-network attack surface rather than internet-routable network access.\nAC:L - This is a locking/race use-after-free where the attacker can repeatedly drive HIDP/L2CAP connection teardown and unregister paths through connection close/disconnect behavior. The race is not dependent on a rare configuration or a condition outside attacker influence.\nPR:N - Although the local HIDP management ioctl path is gated by init-namespace CAP_NET_ADMIN, an adjacent malicious Bluetooth HID peer can trigger teardown of an already established HIDP/L2CAP session without privileges on the victim system. Under the higher-severity reasonable Bluetooth-peer scenario, no victim-system privileges are required.\nUI:N - Once the HIDP/L2CAP session exists, triggering the vulnerable unregister/connection-delete race does not require a victim user to perform an action. The peer can cause disconnect/teardown behavior directly.\nS:U - The vulnerability corrupts kernel Bluetooth/L2CAP state within the same kernel security authority. It is not a VM escape, IOMMU bypass, or other scope-changing boundary crossing.\nC:H - The flaw is a kernel use-after-free/list corruption condition involving L2CAP connection/user objects and potentially freed HCI device memory. Kernel UAFs are defensibly treated as enabling high confidentiality impact through memory disclosure primitives.\nI:H - The same UAF/list corruption can be leveraged beyond a crash for heap manipulation and control-flow or data-structure corruption. Kernel memory corruption is therefore high integrity impact.\nA:H - Syzbot reports show KASAN use-after-free crashes in l2cap_unregister_user, and the bug can corrupt lists during connection teardown. A kernel crash/oops is high availability impact."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:21:59.477Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6.84","versionEndExcluding":"6.6.130"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12.20","versionEndExcluding":"6.12.78"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"6.18.20"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"6.19.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"7.0"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.13.8"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-23461","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:08:32.316331Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-362","lang":"en","type":"CWE","description":"CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T18:35:45.372Z"}}]}}}