CVE-2026-43091 (GCVE-0-2026-43091)
Vulnerability from cvelistv5
Published
2026-05-06 07:40
Modified
2026-08-05 12:25
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: xfrm: Wait for RCU readers during policy netns exit xfrm_policy_fini() frees the policy_bydst hash tables after flushing the policy work items and deleting all policies, but it does not wait for concurrent RCU readers to leave their read-side critical sections first. The policy_bydst tables are published via rcu_assign_pointer() and are looked up through rcu_dereference_check(), so netns teardown must also wait for an RCU grace period before freeing the table memory. Fix this by adding synchronize_rcu() before freeing the policy hash tables.
References
Impacted products
Vendor Product Version
Linux Linux Version: e1e551bc56302b80ff930c966f9985095fb1b70d
Version: e1e551bc56302b80ff930c966f9985095fb1b70d
Version: e1e551bc56302b80ff930c966f9985095fb1b70d
Version: e1e551bc56302b80ff930c966f9985095fb1b70d
Version: e1e551bc56302b80ff930c966f9985095fb1b70d
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/xfrm/xfrm_policy.c"
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          ]
        },
        {
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          "product": "Linux",
          "programFiles": [
            "net/xfrm/xfrm_policy.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.9"
            },
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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            },
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              "status": "unaffected",
              "version": "6.12.83",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.18.24",
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              "status": "unaffected",
              "version": "6.19.14",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: Wait for RCU readers during policy netns exit\n\nxfrm_policy_fini() frees the policy_bydst hash tables after flushing the\npolicy work items and deleting all policies, but it does not wait for\nconcurrent RCU readers to leave their read-side critical sections first.\n\nThe policy_bydst tables are published via rcu_assign_pointer() and are\nlooked up through rcu_dereference_check(), so netns teardown must also\nwait for an RCU grace period before freeing the table memory.\n\nFix this by adding synchronize_rcu() before freeing the policy hash tables."
        }
      ],
      "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 - The vulnerable path requires local control of a network namespace/XFRM policy state and concurrent namespace teardown; remote packets can exercise XFRM policy lookups, but a remote attacker cannot normally trigger the required netns exit.\nAC:L - The race is attacker-controllable by creating XFRM policies, generating policy lookups, and tearing down the namespace concurrently; no rare configuration or victim-controlled timing is required beyond winning a repeatable local race.\nPR:L - XFRM netlink operations require CAP_NET_ADMIN in the target network namespace, but an unprivileged local user can obtain that in a new user+network namespace on common userns-enabled systems.\nUI:N - No victim action is required once the local attacker can run code and issue the relevant namespace, netlink, and traffic operations.\nS:U - The impact is within the kernel security authority; this is a standard kernel memory-safety issue rather than a VM, IOMMU, or separate-scope escape.\nC:H - This is a use-after-free of an RCU-published XFRM policy hash table, and stale readers may dereference reallocated attacker-influenced memory during policy lookup.\nI:H - As a kernel UAF in a list traversal path that can reach policy object handling, the freed memory can plausibly be shaped into fake list/policy data and leveraged for kernel memory corruption.\nA:H - At minimum, dereferencing freed hash-table memory during packet or route policy lookup can trigger a kernel oops or panic, causing high availability impact."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:25:52.160Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/b66920a3348c0f63ba18365248fa21fbf0b3a937"
        },
        {
          "url": "https://git.kernel.org/stable/c/438b1f668ad58f46ce699bb48e4698a7839e3f9e"
        },
        {
          "url": "https://git.kernel.org/stable/c/3733fce2871c9bca9dd18a1a23b1432ea215a094"
        },
        {
          "url": "https://git.kernel.org/stable/c/33a3149dd81a1e2f52b80ee1e0fc380b39f3d028"
        },
        {
          "url": "https://git.kernel.org/stable/c/069daad4f2ae9c5c108131995529d5f02392c446"
        }
      ],
      "title": "xfrm: Wait for RCU readers during policy netns exit",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-43091",
    "datePublished": "2026-05-06T07:40:23.955Z",
    "dateReserved": "2026-05-01T14:12:55.984Z",
    "dateUpdated": "2026-08-05T12:25:52.160Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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