{"id":"CVE-2026-98809","state":"PUBLISHED","title":"Bluetooth: hci_sync: don't drain cmd_sync backlog on unregister","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: hci_sync: don't drain cmd_sync backlog on unregister\n\nhci_unregister_dev() disables cmd_work and cmd_timer, then calls\nhci_cmd_sync_clear(), whose cancel_work_sync() waits for\nhci_cmd_sync_work() to return. That worker dequeues and runs every\nentry on cmd_sync_work_list. With cmd_work disabled nothing reaches\nthe controller, so each queued HCI command waits the full\nHCI_CMD_TIMEOUT (2s).\n\nThe backlog has no bound. Userspace can keep queuing MGMT commands\nsuch as MGMT_OP_GET_CLOCK_INFO against a controller that doesn't\nanswer. Closing /dev/vhci then blocks in vhci_release() for\nbacklog * 2s:\n\n  INFO: task syz-executor:5749 blocked for more than 143 seconds.\n   cancel_work_sync\n   hci_cmd_sync_clear\n   hci_unregister_dev\n   vhci_release\n\nIn a local reproduction the backlog held more than 5000 entries,\nwhich comes to hours of hang.\n\nStop the worker from taking new entries once HCI_UNREGISTER is set,\nand wake any request still waiting with -ENODEV before cancelling\nthe work. The entries left over are destroyed with -ECANCELED by the\nexisting sweep in hci_cmd_sync_clear(). They stay on the list until\nthe work has stopped, so hci_cmd_sync_dequeue() and friends still see\nthem. A callback already running may still issue another command,\nwhich delays unregister by at most one timeout per remaining command,\nnot by the whole backlog.","publishedAt":"2026-10-18T15:48:55.913Z","updatedAt":"2026-10-30T12:39:55.898Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"008ee9eb8a11bcabf12c91771dd4f470b082bd44","status":"affected","lessThan":"b06d85b114cc5fa61809f9950bca66502e0e1173","versionType":"git"},{"version":"008ee9eb8a11bcabf12c91771dd4f470b082bd44","status":"affected","lessThan":"b11acfcb5925ed27fae692b27931a1ac732677fb","versionType":"git"},{"version":"008ee9eb8a11bcabf12c91771dd4f470b082bd44","status":"affected","lessThan":"143bde97c4101ae68eb656c87e620c45b07a3090","versionType":"git"},{"version":"008ee9eb8a11bcabf12c91771dd4f470b082bd44","status":"affected","lessThan":"7f16443a30f4e86d84ae4faf057d333b41ddb757","versionType":"git"},{"version":"008ee9eb8a11bcabf12c91771dd4f470b082bd44","status":"affected","lessThan":"e8ba8c9c74d1035042cdf6cb5adf8f59b9b1271c","versionType":"git"},{"version":"008ee9eb8a11bcabf12c91771dd4f470b082bd44","status":"affected","lessThan":"b1f24c1ab52345e810c42a1a81286cb5a7c92252","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bluetooth/hci_sync.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.17","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.17","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.113","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.56","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.10","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/hci_sync.c"]}],"references":["https://git.kernel.org/stable/c/b06d85b114cc5fa61809f9950bca66502e0e1173","https://git.kernel.org/stable/c/b11acfcb5925ed27fae692b27931a1ac732677fb","https://git.kernel.org/stable/c/143bde97c4101ae68eb656c87e620c45b07a3090","https://git.kernel.org/stable/c/7f16443a30f4e86d84ae4faf057d333b41ddb757","https://git.kernel.org/stable/c/e8ba8c9c74d1035042cdf6cb5adf8f59b9b1271c","https://git.kernel.org/stable/c/b1f24c1ab52345e810c42a1a81286cb5a7c92252"],"weaknesses":[],"ingestedAt":"2026-10-30T13:00:06.648Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98809.json","commit":"cb14bf1b43b0c9f05f7f40eae2246263fd430780","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98809","state":"PUBLISHED","datePublished":"2026-10-18T15:48:55.913Z","dateUpdated":"2026-10-30T12:39:55.898Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.371Z"},"containers":{"cna":{"title":"Bluetooth: hci_sync: don't drain cmd_sync backlog on unregister","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: hci_sync: don't drain cmd_sync backlog on unregister\n\nhci_unregister_dev() disables cmd_work and cmd_timer, then calls\nhci_cmd_sync_clear(), whose cancel_work_sync() waits for\nhci_cmd_sync_work() to return. That worker dequeues and runs every\nentry on cmd_sync_work_list. With cmd_work disabled nothing reaches\nthe controller, so each queued HCI command waits the full\nHCI_CMD_TIMEOUT (2s).\n\nThe backlog has no bound. Userspace can keep queuing MGMT commands\nsuch as MGMT_OP_GET_CLOCK_INFO against a controller that doesn't\nanswer. Closing /dev/vhci then blocks in vhci_release() for\nbacklog * 2s:\n\n  INFO: task syz-executor:5749 blocked for more than 143 seconds.\n   cancel_work_sync\n   hci_cmd_sync_clear\n   hci_unregister_dev\n   vhci_release\n\nIn a local reproduction the backlog held more than 5000 entries,\nwhich comes to hours of hang.\n\nStop the worker from taking new entries once HCI_UNREGISTER is set,\nand wake any request still waiting with -ENODEV before cancelling\nthe work. The entries left over are destroyed with -ECANCELED by the\nexisting sweep in hci_cmd_sync_clear(). They stay on the list until\nthe work has stopped, so hci_cmd_sync_dequeue() and friends still see\nthem. A callback already running may still issue another command,\nwhich delays unregister by at most one timeout per remaining command,\nnot by the whole backlog."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"008ee9eb8a11bcabf12c91771dd4f470b082bd44","status":"affected","lessThan":"b06d85b114cc5fa61809f9950bca66502e0e1173","versionType":"git"},{"version":"008ee9eb8a11bcabf12c91771dd4f470b082bd44","status":"affected","lessThan":"b11acfcb5925ed27fae692b27931a1ac732677fb","versionType":"git"},{"version":"008ee9eb8a11bcabf12c91771dd4f470b082bd44","status":"affected","lessThan":"143bde97c4101ae68eb656c87e620c45b07a3090","versionType":"git"},{"version":"008ee9eb8a11bcabf12c91771dd4f470b082bd44","status":"affected","lessThan":"7f16443a30f4e86d84ae4faf057d333b41ddb757","versionType":"git"},{"version":"008ee9eb8a11bcabf12c91771dd4f470b082bd44","status":"affected","lessThan":"e8ba8c9c74d1035042cdf6cb5adf8f59b9b1271c","versionType":"git"},{"version":"008ee9eb8a11bcabf12c91771dd4f470b082bd44","status":"affected","lessThan":"b1f24c1ab52345e810c42a1a81286cb5a7c92252","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bluetooth/hci_sync.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.17","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.17","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.113","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.56","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.10","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/hci_sync.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/b06d85b114cc5fa61809f9950bca66502e0e1173"},{"url":"https://git.kernel.org/stable/c/b11acfcb5925ed27fae692b27931a1ac732677fb"},{"url":"https://git.kernel.org/stable/c/143bde97c4101ae68eb656c87e620c45b07a3090"},{"url":"https://git.kernel.org/stable/c/7f16443a30f4e86d84ae4faf057d333b41ddb757"},{"url":"https://git.kernel.org/stable/c/e8ba8c9c74d1035042cdf6cb5adf8f59b9b1271c"},{"url":"https://git.kernel.org/stable/c/b1f24c1ab52345e810c42a1a81286cb5a7c92252"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:39:55.898Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"6.12.113"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"6.18.56"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"7.2.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}