{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89655", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.743Z", "datePublished": "2026-09-11T19:45:44.841Z", "dateUpdated": "2026-10-19T08:50:26.879Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:50:26.879Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock\n\nlist_for_each_entry() iterates ci->i_cap_flush_list but drops\ni_ceph_lock to send cap messages. During the unlock window,\nhandle_cap_flush_ack() can acquire i_ceph_lock, detach cf entries\nwith tid <= flush_tid from the list, release i_ceph_lock, and free\nthem via ceph_free_cap_flush() outside any lock. When the original\nthread reacquires i_ceph_lock and the for-loop macro advances via\ncf = list_next_entry(cf, i_list), it dereferences cf->i_list.next\non freed memory.\n\nThe race timeline:\n\n __kick_flushing_caps() handle_cap_flush_ack()\n ----------------------- -----------------------\n holds i_ceph_lock <---\n iterates to cf (tid=10)\n prepares FLUSH message\n drops i_ceph_lock <---\n __send_cap() ── FLUSH(tid=10)\n\t MDS sends FLUSH_ACK(tid=10)\n ---> acquires i_ceph_lock\n cf->tid(10) <= flush_tid(10),\n detaches cf from i_cap_flush_list\n drops i_ceph_lock\n ceph_free_cap_flush(cf) <- frees it!\n acquires i_ceph_lock <---\n for-loop advances:\n cf = list_next_entry(cf, i_list)\n -- UAF on freed cf->i_list.next\n\nThe cf was just sent by __kick_flushing_caps itself via __send_cap().\nThe MDS may respond with FLUSH_ACK quickly enough that\nhandle_cap_flush_ack() frees cf before __kick_flushing_caps can\nfinish the iteration.\n\nFix by converting to a manual while loop: save the next pointer\nunder i_ceph_lock before dropping it, then use the saved pointer\nafter reacquiring, so the potentially-freed cf is never accessed again." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL" }, "scenarios": [ { "lang": "en", "value": "AV:N - handle_cap_flush_ack() runs in the ceph-msgr kworker on CEPH_MSG_CLIENT_CAPS FLUSH_ACK from the MDS over TCP; a malicious or compromised MDS frees the ceph_cap_flush while __kick_flushing_caps() still holds that pointer after dropping i_ceph_lock to send FLUSH.\nAC:L - The MDS controls both sides of the race: it can induce kicking without s_mutex (reconnect sets CEPH_I_KICK_FLUSH, then delayed ceph_check_caps or revoke-queued writeback) and immediately send FLUSH_ACK for the known flush tid in the unlock window around __send_cap().\nPR:N - The attacker is the remote MDS peer on an already-connected kernel CephFS client and needs no Linux UID, capability, or init-namespace root on the victim, matching other MDS-driven client CVEs such as CVE-2026-89651.\nUI:N - Once CephFS is mounted (standard in Rook/Kubernetes/OpenStack), cap-flush kicking runs from mdsc delayed work and writeback, and FLUSH_ACK is processed automatically in kworker context with no further victim mount or interactive step at exploit time.\nS:U - The use-after-free is of a ceph_cap_flush object in the host kernel heap and stays inside the same kernel security authority; it does not cross a VM, IOMMU, or sandbox boundary.\nC:H - After ceph_free_cap_flush(), __kick_flushing_caps() does list_next_entry() on the freed cf; reclaiming the dedicated ceph_cap_flush slab with attacker-controlled objects yields a fake next pointer and arbitrary kernel read, scored High per UAF guidance.\nI:H - The iterator then treats the sprayed object as a live ceph_cap_flush (tid, caps, is_capsnap, i_list) and continues sending cap state from it, giving a heap-reuse write and control-flow hijack primitive scored High for use-after-free.\nA:H - Dereferencing freed cf->i_list.next oopses or panics the kicker thread even without full exploitation, and a malicious MDS can retrigger the race on every cap flush." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/ceph/caps.c" ], "versions": [ { "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "091137821e1fc88f37e15201abf055c9494ddc61", "status": "affected", "versionType": "git" }, { "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "01542430081014d80fc9e70e92d6647432ddb7fc", "status": "affected", "versionType": "git" }, { "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "23eb34a53a53cb1a6dab1eeee830633207ac158d", "status": "affected", "versionType": "git" }, { "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "19f16f04c2b014a7dd214dc1e42557d8530b16f3", "status": "affected", "versionType": "git" }, { "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "2701431aa3cc8b23efe6890182e7b04f5e76fab5", "status": "affected", "versionType": "git" }, { "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "fe46746087b5b9c5bb2d022df6c7819218494ced", "status": "affected", "versionType": "git" }, { "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "2dba24dcd5050be4b7b119e6f0b01f62203b5d26", "status": "affected", "versionType": "git" }, { "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "7af4c4f01305b0935adf6d4301b1ec407025485d", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/ceph/caps.c" ], "versions": [ { "version": "4.8", "status": "affected" }, { "version": "0", "lessThan": "4.8", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.270", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.221", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.188", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.157", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.109", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.50", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.4", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "5.10.270" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "5.15.221" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.1.188" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.6.157" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.12.109" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.18.50" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/091137821e1fc88f37e15201abf055c9494ddc61" }, { "url": "https://git.kernel.org/stable/c/01542430081014d80fc9e70e92d6647432ddb7fc" }, { "url": "https://git.kernel.org/stable/c/23eb34a53a53cb1a6dab1eeee830633207ac158d" }, { "url": "https://git.kernel.org/stable/c/19f16f04c2b014a7dd214dc1e42557d8530b16f3" }, { "url": "https://git.kernel.org/stable/c/2701431aa3cc8b23efe6890182e7b04f5e76fab5" }, { "url": "https://git.kernel.org/stable/c/fe46746087b5b9c5bb2d022df6c7819218494ced" }, { "url": "https://git.kernel.org/stable/c/2dba24dcd5050be4b7b119e6f0b01f62203b5d26" }, { "url": "https://git.kernel.org/stable/c/7af4c4f01305b0935adf6d4301b1ec407025485d" } ], "title": "ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2026-89655", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "yes" }, { "Technical Impact": "total" } ], "version": "2.0.3", "timestamp": "2026-10-16T19:25:27.776156Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T19:26:47.285Z" } } ] } }