CVE-2026-97611 (GCVE-0-2026-97611)

Vulnerability from cvelistv5 – Published: 2026-09-25 10:22 – Updated: 2026-09-25 14:41
VLAI
Title
net: openvswitch: fix use-after-free of the flow table mask array
Summary
In the Linux kernel, the following vulnerability has been resolved: net: openvswitch: fix use-after-free of the flow table mask array tbl_mask_array_realloc() retires the old mask_array before it stops being reachable: old = ovsl_dereference(tbl->mask_array); if (old) { ... call_rcu(&old->rcu, mask_array_rcu_cb); } rcu_assign_pointer(tbl->mask_array, new); call_rcu() only waits for read-side critical sections already in flight. tbl->mask_array still points at old between the call_rcu() and the rcu_assign_pointer(), so a reader entering ovs_flow_tbl_lookup_stats() in that window picks up old in a fresh critical section that the pending grace period does not cover. tbl_mask_array_realloc() runs in process context under ovs_mutex, so the window is preemptible and can outlast the grace period. Then mask_array_rcu_cb() frees old before the swap runs: BUG: KASAN: slab-use-after-free in flow_lookup.constprop.0+0x2bf/0x2f0 Read of size 8 at addr ffff888020b3e018 by task poc/741 flow_lookup.constprop.0+0x2bf/0x2f0 ovs_flow_tbl_lookup_stats+0x4a3/0x5c0 ovs_dp_process_packet+0x19c/0x710 ovs_vport_receive+0x243/0x390 internal_dev_xmit+0x81/0x170 Freed by task 728: kfree+0x16a/0x4e0 rcu_core+0x853/0x1030 Publish the new array before retiring the old one. The kfree_rcu() that call_rcu() replaced ran after the swap.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: eac87c413bf9794c14d488998a5265ea5b32f04e , < cd982e11684def5d4a9fcfd5354de09032828414 (git)
Affected: eac87c413bf9794c14d488998a5265ea5b32f04e , < a0d18d21d48a551f82ee344e50efb8a682161489 (git)
Affected: eac87c413bf9794c14d488998a5265ea5b32f04e , < 035e9c3722067648a99010711d0ce81f42572ef4 (git)
Affected: eac87c413bf9794c14d488998a5265ea5b32f04e , < ba4ba11ed6eb8972c69070417fc27b48deb002e8 (git)
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Linux Linux Affected: 5.9
Unaffected: 0 , < 5.9 (semver)
Unaffected: 6.12.111 , ≤ 6.12.* (semver)
Unaffected: 6.18.53 , ≤ 6.18.* (semver)
Unaffected: 7.2.7 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc3 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/openvswitch/flow_table.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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        {
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          "product": "Linux",
          "programFiles": [
            "net/openvswitch/flow_table.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "5.9"
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.12.111",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.53",
              "versionType": "semver"
            },
            {
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              "status": "unaffected",
              "version": "7.2.7",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
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          "nodes": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.111",
                  "versionStartIncluding": "5.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.53",
                  "versionStartIncluding": "5.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.7",
                  "versionStartIncluding": "5.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc3",
                  "versionStartIncluding": "5.9",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: openvswitch: fix use-after-free of the flow table mask array\n\ntbl_mask_array_realloc() retires the old mask_array before it stops being\nreachable:\n\n\told = ovsl_dereference(tbl-\u003emask_array);\n\tif (old) {\n\t\t...\n\t\tcall_rcu(\u0026old-\u003ercu, mask_array_rcu_cb);\n\t}\n\n\trcu_assign_pointer(tbl-\u003emask_array, new);\n\ncall_rcu() only waits for read-side critical sections already in flight.\ntbl-\u003emask_array still points at old between the call_rcu() and the\nrcu_assign_pointer(), so a reader entering ovs_flow_tbl_lookup_stats() in\nthat window picks up old in a fresh critical section that the pending\ngrace period does not cover.\n\ntbl_mask_array_realloc() runs in process context under ovs_mutex, so the\nwindow is preemptible and can outlast the grace period. Then\nmask_array_rcu_cb() frees old before the swap runs:\n\n  BUG: KASAN: slab-use-after-free in flow_lookup.constprop.0+0x2bf/0x2f0\n  Read of size 8 at addr ffff888020b3e018 by task poc/741\n   flow_lookup.constprop.0+0x2bf/0x2f0\n   ovs_flow_tbl_lookup_stats+0x4a3/0x5c0\n   ovs_dp_process_packet+0x19c/0x710\n   ovs_vport_receive+0x243/0x390\n   internal_dev_xmit+0x81/0x170\n  Freed by task 728:\n   kfree+0x16a/0x4e0\n   rcu_core+0x853/0x1030\n\nPublish the new array before retiring the old one. The kfree_rcu() that\ncall_rcu() replaced ran after the swap."
        }
      ],
      "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 - Both sides of the race are driven locally: tbl_mask_array_realloc() runs from OVS_FLOW_CMD_NEW/DEL generic-netlink requests (flow insert/remove growing or shrinking the mask array), and the reader is ovs_flow_tbl_lookup_stats() fed by the attacker\u0027s own packets via internal_dev_xmit. No remote protocol carries data that causes the bug.\nAC:L - The attacker controls both sides, looping flow add/delete to trigger reallocs while transmitting on the datapath\u0027s internal port so lookups run. Failed attempts are harmless, the preemptible window can outlast a grace period, and the reporter\u0027s KASAN trace shows a PoC hit it.\nPR:L - The OVS datapath, vport and flow genl ops are GENL_UNS_ADMIN_PERM with netnsok=true, so CAP_NET_ADMIN in a user namespace (unshare -Urn) is enough to create a datapath, add flows and send packets through it.\nUI:N - No victim action is needed; the attacker creates the datapath, drives mask-array reallocation and generates the lookup traffic entirely by themselves.\nS:U - The impact stays within the kernel\u0027s own security authority, as ordinary kernel memory corruption leading to local privilege escalation; no VM or hardware boundary is crossed.\nC:H - flow_lookup() reads the freed struct mask_array (max, masks[] pointers) and dereferences masks[i] as sw_flow_mask. If the slab is reclaimed with attacker data, that gives controlled-pointer reads of kernel memory.\nI:H - On a flow hit, flow_lookup() does stats-\u003eusage_cntrs[index]++ through ma-\u003emasks_usage_stats taken from the freed mask_array, so a reclaimed object yields an attacker-steered kernel memory increment (write primitive).\nA:H - The slab use-after-free in flow_lookup() during ovs_dp_process_packet crashes the kernel (KASAN-reported); with a reclaimed object, wild pointer dereferences cause an oops or panic."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-25T14:41:33.156Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/cd982e11684def5d4a9fcfd5354de09032828414"
        },
        {
          "url": "https://git.kernel.org/stable/c/a0d18d21d48a551f82ee344e50efb8a682161489"
        },
        {
          "url": "https://git.kernel.org/stable/c/035e9c3722067648a99010711d0ce81f42572ef4"
        },
        {
          "url": "https://git.kernel.org/stable/c/ba4ba11ed6eb8972c69070417fc27b48deb002e8"
        }
      ],
      "title": "net: openvswitch: fix use-after-free of the flow table mask array",
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        "engine": "bippy-1.2.0"
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-97611",
    "datePublished": "2026-09-25T10:22:20.827Z",
    "dateReserved": "2026-09-24T16:01:01.158Z",
    "dateUpdated": "2026-09-25T14:41:33.156Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-97611",
      "date": "2026-09-28",
      "epss": "0.00159",
      "percentile": "0.04304"
    },
    "microsoft_vex": {
      "current_release_date": "2026-09-28T02:49:18.000Z",
      "cve": "CVE-2026-97611",
      "id": "msrc_CVE-2026-97611",
      "initial_release_date": "2026-09-28T02:49:18.000Z",
      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "net: openvswitch: fix use-after-free of the flow table mask array",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-97611.json",
      "version": "1"
    },
    "nvd": {
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        "affected": [
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                  "net/openvswitch/flow_table.c"
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                ]
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                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
                "versions": [
                  {
                    "status": "affected",
                    "version": "5.9"
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                  {
                    "lessThan": "5.9",
                    "status": "unaffected",
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                    "versionType": "semver"
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                    "versionType": "semver"
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                    "versionType": "semver"
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            ],
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: openvswitch: fix use-after-free of the flow table mask array\n\ntbl_mask_array_realloc() retires the old mask_array before it stops being\nreachable:\n\n\told = ovsl_dereference(tbl-\u003emask_array);\n\tif (old) {\n\t\t...\n\t\tcall_rcu(\u0026old-\u003ercu, mask_array_rcu_cb);\n\t}\n\n\trcu_assign_pointer(tbl-\u003emask_array, new);\n\ncall_rcu() only waits for read-side critical sections already in flight.\ntbl-\u003emask_array still points at old between the call_rcu() and the\nrcu_assign_pointer(), so a reader entering ovs_flow_tbl_lookup_stats() in\nthat window picks up old in a fresh critical section that the pending\ngrace period does not cover.\n\ntbl_mask_array_realloc() runs in process context under ovs_mutex, so the\nwindow is preemptible and can outlast the grace period. Then\nmask_array_rcu_cb() frees old before the swap runs:\n\n  BUG: KASAN: slab-use-after-free in flow_lookup.constprop.0+0x2bf/0x2f0\n  Read of size 8 at addr ffff888020b3e018 by task poc/741\n   flow_lookup.constprop.0+0x2bf/0x2f0\n   ovs_flow_tbl_lookup_stats+0x4a3/0x5c0\n   ovs_dp_process_packet+0x19c/0x710\n   ovs_vport_receive+0x243/0x390\n   internal_dev_xmit+0x81/0x170\n  Freed by task 728:\n   kfree+0x16a/0x4e0\n   rcu_core+0x853/0x1030\n\nPublish the new array before retiring the old one. The kfree_rcu() that\ncall_rcu() replaced ran after the swap."
          }
        ],
        "id": "CVE-2026-97611",
        "lastModified": "2026-09-25T15:18:01.373",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 1.8,
              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
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        "published": "2026-09-25T11:17:15.213",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/035e9c3722067648a99010711d0ce81f42572ef4"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/a0d18d21d48a551f82ee344e50efb8a682161489"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/cd982e11684def5d4a9fcfd5354de09032828414"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    }
  }
}



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