CVE-2026-72389 (GCVE-0-2026-72389)
Vulnerability from cvelistv5
Published
2026-08-15 05:56
Modified
2026-08-17 05:43
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: bridge: stp: Fix a potential use-after-free when deleting a bridge The three STP timers are not supposed to be armed while the bridge is administratively down. They are synchronously deactivated when the bridge is put administratively down and the various call sites check for 'IFF_UP' before arming them. This check is missing from br_topology_change_detection() and it is possible to engineer a situation in which the topology change timer is armed while the bridge is administratively down, resulting in a use-after-free [1] when the bridge is deleted. Fix by adding the missing check and for good measures synchronously shutdown the three timers when the bridge is deleted. [1] ODEBUG: free active (active state 0) object: ffff88811662b9b0 object type: timer_list hint: br_topology_change_timer_expired (net/bridge/br_stp_timer.c:120) WARNING: lib/debugobjects.c:629 at debug_print_object+0x1bc/0x450, CPU#9: ip/359
References
Impacted products
Vendor Product Version
Linux Linux Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/bridge/br_if.c",
            "net/bridge/br_stp.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "lessThan": "c86579b0a2d201792bcb59316629f4ba4758cfc8",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
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              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
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              "status": "affected",
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            {
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              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/bridge/br_if.c",
            "net/bridge/br_stp.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.12"
            },
            {
              "lessThan": "2.6.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.212",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.178",
              "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": "5.15.212",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.178",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.145",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.97",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.40",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.5",
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                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbridge: stp: Fix a potential use-after-free when deleting a bridge\n\nThe three STP timers are not supposed to be armed while the bridge is\nadministratively down. They are synchronously deactivated when the\nbridge is put administratively down and the various call sites check for\n\u0027IFF_UP\u0027 before arming them.\n\nThis check is missing from br_topology_change_detection() and it is\npossible to engineer a situation in which the topology change timer is\narmed while the bridge is administratively down, resulting in a\nuse-after-free [1] when the bridge is deleted.\n\nFix by adding the missing check and for good measures synchronously\nshutdown the three timers when the bridge is deleted.\n\n[1]\nODEBUG: free active (active state 0) object: ffff88811662b9b0 object type: timer_list hint: br_topology_change_timer_expired (net/bridge/br_stp_timer.c:120)\nWARNING: lib/debugobjects.c:629 at debug_print_object+0x1bc/0x450, CPU#9: ip/359"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Exploitation is via local RTNETLINK/ioctl to create a down bridge, enable kernel STP, enslave ports, and delete the bridge; remote STP BPDU handling is blocked when IFF_UP is clear, so the arming path that leaves timers active on a down bridge is local.\nAC:L - The public PoC uses a reliable, attacker-controlled netlink sequence (down bridge + kernel STP + port state progression + dellink) without winning races; per-port forward-delay timers deterministically reach br_topology_change_detection and arm topology_change_timer before deletion.\nPR:L - All reachable paths (RTM_NEWLINK/DELLINK, IFLA_BR_STP_STATE, enslaving ports) require CAP_NET_ADMIN, which unprivileged users can obtain in user/network namespaces (unshare -Urn, Kubernetes NET_ADMIN, LXC/libvirt network namespaces).\nUI:N - Triggering requires only programmatic bridge configuration by the attacker; no victim must click, mount, or open anything beyond the attacker\u0027s own netlink operations.\nS:U - Impact is kernel memory corruption and privilege escalation within the same kernel/host security domain; it does not cross a VM, container-to-host, or IOMMU boundary by itself.\nC:H - Use-after-free of the net_device/net_bridge kmalloc object lets an attacker reclaim freed slab memory and obtain arbitrary kernel read/disclosure primitives from corrupted timer and bridge structures.\nI:H - Disclosed analysis and PoC show the dangling timer callback can hijack control flow by reclaiming the freed object with attacker-controlled data, replacing the timer function pointer for arbitrary kernel code execution.\nA:H - Deleting the bridge with active STP timers queued causes the per-CPU timer wheel to invoke callbacks on freed memory, producing kernel BUG/oops/panics and denial of service even if full exploitation is not attempted."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:43:35.297Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/c86579b0a2d201792bcb59316629f4ba4758cfc8"
        },
        {
          "url": "https://git.kernel.org/stable/c/297a747f59bff6573196d7236178144d66524e68"
        },
        {
          "url": "https://git.kernel.org/stable/c/4c40eec06eeac37c58e47a6058eb32901218d5d4"
        },
        {
          "url": "https://git.kernel.org/stable/c/39283907a25e5caf0f2bd2947f6e56644b01e2b7"
        },
        {
          "url": "https://git.kernel.org/stable/c/b4b3458ef88df4798632619f018791d4344bcd92"
        },
        {
          "url": "https://git.kernel.org/stable/c/40cbfa3a28e0919469d1b086629bb3ce38a83593"
        },
        {
          "url": "https://git.kernel.org/stable/c/2a00517db8de4be7df3d483b215c5544fb30a191"
        }
      ],
      "title": "bridge: stp: Fix a potential use-after-free when deleting a bridge",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-72389",
    "datePublished": "2026-08-15T05:56:18.553Z",
    "dateReserved": "2026-08-09T03:40:39.923Z",
    "dateUpdated": "2026-08-17T05:43:35.297Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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