{"id":"CVE-2026-74401","state":"PUBLISHED","title":"dlm: fix add msg handle in send_queue ordered","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ndlm: fix add msg handle in send_queue ordered\n\nIn a benchmark scenario triggering a lot of requests that triggers a lot\nof DLM messages on the network it can be that the mh->seq is not ordered\naccording the oldest seq number. This ordering is required by\ndlm_receive_ack as \"before(mh->seq, seq)\" will stop to check for older\nsequence numbers that are ordered in the tail of \"node->send_queue\".\n\nThe side effects of not having it correct ordered regarding\n\"before(mh->seq, seq)\" are refcounting issues and use-after free.\n\nI only was able to reproduce this issue in a experimental DLM branch\nand a user space DLM benchmark that uses io_uring. After changing this I\ndon't experienced any refcounting with the sending buffer issues anymore.","publishedAt":"2026-08-15T05:59:12.099Z","updatedAt":"2026-10-30T12:29:57.496Z","severity":{"score":9.8,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/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":"489d8e559c6596eb08e16447d9830bc39afbe54e","status":"affected","lessThan":"482606fea302d8bab86901d7426c3716980d99a8","versionType":"git"},{"version":"489d8e559c6596eb08e16447d9830bc39afbe54e","status":"affected","lessThan":"ae9e534e502a0f48c12baf83608c5de0ff0eab11","versionType":"git"},{"version":"489d8e559c6596eb08e16447d9830bc39afbe54e","status":"affected","lessThan":"6369619f1b665f12d8c99cc6ff733c64eb08b22e","versionType":"git"},{"version":"489d8e559c6596eb08e16447d9830bc39afbe54e","status":"affected","lessThan":"712714f818d83373847874ab0f8e426be79296cf","versionType":"git"},{"version":"489d8e559c6596eb08e16447d9830bc39afbe54e","status":"affected","lessThan":"4d45250b1d22960f86d83245be188b16e456218b","versionType":"git"},{"version":"489d8e559c6596eb08e16447d9830bc39afbe54e","status":"affected","lessThan":"d2248cb70c070f8f04762872772e155b59016f17","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/dlm/midcomms.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.14","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/dlm/midcomms.c"]}],"references":["https://git.kernel.org/stable/c/482606fea302d8bab86901d7426c3716980d99a8","https://git.kernel.org/stable/c/ae9e534e502a0f48c12baf83608c5de0ff0eab11","https://git.kernel.org/stable/c/6369619f1b665f12d8c99cc6ff733c64eb08b22e","https://git.kernel.org/stable/c/712714f818d83373847874ab0f8e426be79296cf","https://git.kernel.org/stable/c/4d45250b1d22960f86d83245be188b16e456218b","https://git.kernel.org/stable/c/d2248cb70c070f8f04762872772e155b59016f17"],"weaknesses":[],"ingestedAt":"2026-10-30T12:48:04.825Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/74xxx/CVE-2026-74401.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-74401","state":"PUBLISHED","datePublished":"2026-08-15T05:59:12.099Z","dateUpdated":"2026-10-30T12:29:57.496Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-15T05:44:03.892Z"},"containers":{"cna":{"title":"dlm: fix add msg handle in send_queue ordered","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ndlm: fix add msg handle in send_queue ordered\n\nIn a benchmark scenario triggering a lot of requests that triggers a lot\nof DLM messages on the network it can be that the mh->seq is not ordered\naccording the oldest seq number. This ordering is required by\ndlm_receive_ack as \"before(mh->seq, seq)\" will stop to check for older\nsequence numbers that are ordered in the tail of \"node->send_queue\".\n\nThe side effects of not having it correct ordered regarding\n\"before(mh->seq, seq)\" are refcounting issues and use-after free.\n\nI only was able to reproduce this issue in a experimental DLM branch\nand a user space DLM benchmark that uses io_uring. After changing this I\ndon't experienced any refcounting with the sending buffer issues anymore."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"489d8e559c6596eb08e16447d9830bc39afbe54e","status":"affected","lessThan":"482606fea302d8bab86901d7426c3716980d99a8","versionType":"git"},{"version":"489d8e559c6596eb08e16447d9830bc39afbe54e","status":"affected","lessThan":"ae9e534e502a0f48c12baf83608c5de0ff0eab11","versionType":"git"},{"version":"489d8e559c6596eb08e16447d9830bc39afbe54e","status":"affected","lessThan":"6369619f1b665f12d8c99cc6ff733c64eb08b22e","versionType":"git"},{"version":"489d8e559c6596eb08e16447d9830bc39afbe54e","status":"affected","lessThan":"712714f818d83373847874ab0f8e426be79296cf","versionType":"git"},{"version":"489d8e559c6596eb08e16447d9830bc39afbe54e","status":"affected","lessThan":"4d45250b1d22960f86d83245be188b16e456218b","versionType":"git"},{"version":"489d8e559c6596eb08e16447d9830bc39afbe54e","status":"affected","lessThan":"d2248cb70c070f8f04762872772e155b59016f17","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/dlm/midcomms.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.14","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/dlm/midcomms.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/482606fea302d8bab86901d7426c3716980d99a8"},{"url":"https://git.kernel.org/stable/c/ae9e534e502a0f48c12baf83608c5de0ff0eab11"},{"url":"https://git.kernel.org/stable/c/6369619f1b665f12d8c99cc6ff733c64eb08b22e"},{"url":"https://git.kernel.org/stable/c/712714f818d83373847874ab0f8e426be79296cf"},{"url":"https://git.kernel.org/stable/c/4d45250b1d22960f86d83245be188b16e456218b"},{"url":"https://git.kernel.org/stable/c/d2248cb70c070f8f04762872772e155b59016f17"}],"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 - The UAF is triggered in dlm_receive_ack when processing DLM_ACK packets from remote cluster peers over lowcomms TCP/SCTP port 21064 (receive_from_sock -> dlm_process_incoming_buffer -> dlm_midcomms_receive_buffer_3_2); wire ACK sequence numbers directly drive premature dlm_mhandle_delete on the victim.\nAC:L - The send_queue ordering race in midcomms_new_msg_cb is hit under heavy concurrent DLM traffic; an attacker controls both sides by flooding lock requests from a cluster peer (io_uring benchmark per fix author) while sending ACKs, without depending on timing they cannot influence.\nPR:N - DLM has no authentication or TLS; the only gate is source IP matching a configured cluster node in addr_to_nodeid. A compromised cluster peer or attacker on the cluster network needs no Unix account or local privileges on the victim to deliver crafted DLM_ACK packets.\nUI:N - No victim user action is required; ACKs and lock traffic are processed automatically on already-running HA cluster nodes (GFS2/OCFS2/Pacemaker) by DLM receive and send workqueues without any interactive step.\nS:U - Impact is confined to kernel heap and refcount corruption within the victim node's kernel address space; no VM, IOMMU, or sandbox boundary is crossed—standard kernel UAF enabling privilege escalation on the same host.\nC:H - Misordered send_queue causes dlm_receive_ack to skip or prematurely free mhandles via call_rcu/dlm_mhandle_release while references still exist; UAF reads from freed slab objects enable heap grooming and arbitrary kernel memory disclosure.\nI:H - Premature dlm_mhandle_delete releases in-flight mh->msg buffers and corrupts kref counts while commit paths still dereference the handle; UAF write primitives via reclaimed slab data can hijack kernel control flow per DLM UAF scoring guidance.\nA:H - Refcounting corruption and use-after-free in dlm_receive_ack reliably cause KASAN splats, kernel oopses, and cluster-wide availability loss when DLM on HA nodes handling GFS2/OCFS2 lock traffic crashes or hangs."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:29:57.496Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"6.6.145"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"6.12.97"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"6.18.40"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"7.1.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-74401","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T18:55:33.158512Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-16T19:05:42.033Z"}}]}}}