{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-74401", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-15T05:44:03.892Z", "datePublished": "2026-08-15T05:59:12.099Z", "dateUpdated": "2026-08-17T05:46:44.230Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T05:46:44.230Z" }, "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." } ], "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." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/dlm/midcomms.c" ], "versions": [ { "version": "489d8e559c6596eb08e16447d9830bc39afbe54e", "lessThan": "ae9e534e502a0f48c12baf83608c5de0ff0eab11", "status": "affected", "versionType": "git" }, { "version": "489d8e559c6596eb08e16447d9830bc39afbe54e", "lessThan": "6369619f1b665f12d8c99cc6ff733c64eb08b22e", "status": "affected", "versionType": "git" }, { "version": "489d8e559c6596eb08e16447d9830bc39afbe54e", "lessThan": "712714f818d83373847874ab0f8e426be79296cf", "status": "affected", "versionType": "git" }, { "version": "489d8e559c6596eb08e16447d9830bc39afbe54e", "lessThan": "4d45250b1d22960f86d83245be188b16e456218b", "status": "affected", "versionType": "git" }, { "version": "489d8e559c6596eb08e16447d9830bc39afbe54e", "lessThan": "d2248cb70c070f8f04762872772e155b59016f17", "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/dlm/midcomms.c" ], "versions": [ { "version": "5.14", "status": "affected" }, { "version": "0", "lessThan": "5.14", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.145", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.97", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.40", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.5", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "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": "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" } ] } ] } ], "references": [ { "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" } ], "title": "dlm: fix add msg handle in send_queue ordered", "x_generator": { "engine": "bippy-1.2.0" } } } }