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

Vulnerability from cvelistv5 – Published: 2026-08-15 05:59 – Updated: 2026-08-17 05:46
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
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 489d8e559c6596eb08e16447d9830bc39afbe54e , < ae9e534e502a0f48c12baf83608c5de0ff0eab11 (git)
Affected: 489d8e559c6596eb08e16447d9830bc39afbe54e , < 6369619f1b665f12d8c99cc6ff733c64eb08b22e (git)
Affected: 489d8e559c6596eb08e16447d9830bc39afbe54e , < 712714f818d83373847874ab0f8e426be79296cf (git)
Affected: 489d8e559c6596eb08e16447d9830bc39afbe54e , < 4d45250b1d22960f86d83245be188b16e456218b (git)
Affected: 489d8e559c6596eb08e16447d9830bc39afbe54e , < d2248cb70c070f8f04762872772e155b59016f17 (git)
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Linux Linux Affected: 5.14
Unaffected: 0 , < 5.14 (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)
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          "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."
        }
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              "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."
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    "dateReserved": "2026-08-15T05:44:03.892Z",
    "dateUpdated": "2026-08-17T05:46:44.230Z",
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            "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."
          }
        ],
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        "lastModified": "2026-08-17T06:19:35.270",
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                "baseScore": 9.8,
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                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
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        "published": "2026-08-15T06:22:42.120",
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      "current_release_date": "2026-08-20T22:18:04+00:00",
      "cve": "CVE-2026-74401",
      "id": "CVE-2026-74401",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "122",
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      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: dlm: fix add msg handle in send_queue ordered",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74401.json",
      "version": "3"
    },
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      "current_release_date": "2026-09-15T01:21:32Z",
      "cve": "CVE-2026-74401",
      "id": "CVE-2026-74401",
      "initial_release_date": "2026-08-31T13:29:22Z",
      "product_status:known_affected": "219",
      "product_status:known_not_affected": "143",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-74401",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-74401.json",
      "version": "4"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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