CVE-2026-97611 (GCVE-0-2026-97611)
Vulnerability from cvelistv5
Published
2026-09-25 10:22
Modified
2026-10-19 09:10
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: 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.
References
Impacted products
Vendor Product Version
Linux Linux Version: eac87c413bf9794c14d488998a5265ea5b32f04e
Version: eac87c413bf9794c14d488998a5265ea5b32f04e
Version: eac87c413bf9794c14d488998a5265ea5b32f04e
Version: eac87c413bf9794c14d488998a5265ea5b32f04e
Version: eac87c413bf9794c14d488998a5265ea5b32f04e
Version: eac87c413bf9794c14d488998a5265ea5b32f04e
Version: eac87c413bf9794c14d488998a5265ea5b32f04e
Version: eac87c413bf9794c14d488998a5265ea5b32f04e
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/openvswitch/flow_table.c"
          ],
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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              "version": "6.12.111",
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              "version": "7.2.7",
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              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "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": "2026-10-19T09:10:15.022Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/4c98b492e9ed63f9ca3e23566d9a6a4f235944f4"
        },
        {
          "url": "https://git.kernel.org/stable/c/4016ead17acd75312c066ecd47c4b7f0a81ceaa2"
        },
        {
          "url": "https://git.kernel.org/stable/c/017dbbf0d6c319a487f68e22f56d91fc787d5525"
        },
        {
          "url": "https://git.kernel.org/stable/c/76678217cdabc41e3c74c23b45b62086ffb8fe7a"
        },
        {
          "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",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "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": "2026-10-19T09:10:15.022Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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