CVE-2026-74401 (GCVE-0-2026-74401)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:59 – Updated: 2026-10-30 12:29
VLAI
Title
dlm: fix add msg handle in send_queue ordered
Summary
In the Linux kernel, the following vulnerability has been resolved: dlm: fix add msg handle in send_queue ordered In a benchmark scenario triggering a lot of requests that triggers a lot of DLM messages on the network it can be that the mh->seq is not ordered according the oldest seq number. This ordering is required by dlm_receive_ack as "before(mh->seq, seq)" will stop to check for older sequence numbers that are ordered in the tail of "node->send_queue". The side effects of not having it correct ordered regarding "before(mh->seq, seq)" are refcounting issues and use-after free. I only was able to reproduce this issue in a experimental DLM branch and a user space DLM benchmark that uses io_uring. After changing this I don't experienced any refcounting with the sending buffer issues anymore.
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: yes Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 18:55 UTC
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6641 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 489d8e559c6596eb08e16447d9830bc39afbe54e , < 482606fea302d8bab86901d7426c3716980d99a8 (git)
Affected: 489d8e559c6596eb08e16447d9830bc39afbe54e , < ae9e534e502a0f48c12baf83608c5de0ff0eab11 (git)
Affected: 489d8e559c6596eb08e16447d9830bc39afbe54e , < 6369619f1b665f12d8c99cc6ff733c64eb08b22e (git)
Affected: 489d8e559c6596eb08e16447d9830bc39afbe54e , < 712714f818d83373847874ab0f8e426be79296cf (git)
Affected: 489d8e559c6596eb08e16447d9830bc39afbe54e , < 4d45250b1d22960f86d83245be188b16e456218b (git)
Affected: 489d8e559c6596eb08e16447d9830bc39afbe54e , < d2248cb70c070f8f04762872772e155b59016f17 (git)
guessed Create a notification for this product.
Linux Linux Affected: 5.14
Unaffected: 0 , < 5.14 (semver)
Unaffected: 6.1.191 , ≤ 6.1.* (semver)
Unaffected: 6.6.145 , ≤ 6.6.* (semver)
Unaffected: 6.12.97 , ≤ 6.12.* (semver)
Unaffected: 6.18.40 , ≤ 6.18.* (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "lessThan": "ae9e534e502a0f48c12baf83608c5de0ff0eab11",
                  "status": "affected",
                  "version": "489d8e559c6596eb08e16447d9830bc39afbe54e",
                  "versionType": "git"
                },
                {
                  "lessThan": "6369619f1b665f12d8c99cc6ff733c64eb08b22e",
                  "status": "affected",
                  "version": "489d8e559c6596eb08e16447d9830bc39afbe54e",
                  "versionType": "git"
                },
                {
                  "lessThan": "712714f818d83373847874ab0f8e426be79296cf",
                  "status": "affected",
                  "version": "489d8e559c6596eb08e16447d9830bc39afbe54e",
                  "versionType": "git"
                },
                {
                  "lessThan": "4d45250b1d22960f86d83245be188b16e456218b",
                  "status": "affected",
                  "version": "489d8e559c6596eb08e16447d9830bc39afbe54e",
                  "versionType": "git"
                },
                {
                  "lessThan": "d2248cb70c070f8f04762872772e155b59016f17",
                  "status": "affected",
                  "version": "489d8e559c6596eb08e16447d9830bc39afbe54e",
                  "versionType": "git"
                }
              ]
            },
            {
              "defaultStatus": "affected",
              "product": "Linux",
              "programFiles": [
                "fs/dlm/midcomms.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "status": "affected",
                  "version": "5.14"
                },
                {
                  "lessThan": "5.14",
                  "status": "unaffected",
                  "version": "0",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.6.*",
                  "status": "unaffected",
                  "version": "6.6.145",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.12.*",
                  "status": "unaffected",
                  "version": "6.12.97",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.18.*",
                  "status": "unaffected",
                  "version": "6.18.40",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "7.1.*",
                  "status": "unaffected",
                  "version": "7.1.5",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "*",
                  "status": "unaffected",
                  "version": "7.2",
                  "versionType": "original_commit_for_fix"
                }
              ]
            }
          ],
          "cpeApplicability": [
            {
              "nodes": [
                {
                  "cpeMatch": [
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.6.145",
                      "versionStartIncluding": "5.14",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.12.97",
                      "versionStartIncluding": "5.14",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.18.40",
                      "versionStartIncluding": "5.14",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "7.1.5",
                      "versionStartIncluding": "5.14",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "7.2",
                      "versionStartIncluding": "5.14",
                      "vulnerable": true
                    }
                  ],
                  "negate": false,
                  "operator": "OR"
                }
              ]
            }
          ],
          "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-\u003eseq is not ordered\naccording the oldest seq number. This ordering is required by\ndlm_receive_ack as \"before(mh-\u003eseq, seq)\" will stop to check for older\nsequence numbers that are ordered in the tail of \"node-\u003esend_queue\".\n\nThe side effects of not having it correct ordered regarding\n\"before(mh-\u003eseq, 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\u0027t experienced any refcounting with the sending buffer issues anymore."
            }
          ],
          "metrics": [
            {
              "cvssV3_1": {
                "baseScore": 9.8,
                "baseSeverity": "CRITICAL",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "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 -\u003e dlm_process_incoming_buffer -\u003e 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\u0027s kernel address space; no VM, IOMMU, or sandbox boundary is crossed\u2014standard 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-\u003emsg 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": {
            "dateUpdated": "2026-08-17T05:46:44.230Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
          },
          "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"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2026-74401",
        "datePublished": "2026-08-15T05:59:12.099Z",
        "dateReserved": "2026-08-15T05:44:03.892Z",
        "dateUpdated": "2026-10-16T19:05:42.033Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Sightings

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Nomenclature

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Vulnerability timeline

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