Vulnerability-Lookup

FKIE_CVE-2026-72137

Vulnerability from fkie_nvd - Published: 2026-08-15 06:21 - Updated: 2026-08-17 06:18

Severity

9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Summary

In the Linux kernel, the following vulnerability has been resolved: xfrm: nat_keepalive: avoid double free on send error nat_keepalive_send() frees the keepalive skb whenever the IPv4 or IPv6 send helper reports an error. That cleanup is only correct before the skb is handed to the output path. Once ip_build_and_send_pkt() or ip6_xmit() takes ownership, the networking stack may already have consumed the skb before returning an error, so freeing it again is unsafe. Handle the pre-handoff failure cases inside nat_keepalive_send_ipv4() and nat_keepalive_send_ipv6(), where the caller still owns the skb, and keep nat_keepalive_send() responsible only for family dispatch and the unsupported-family cleanup path.

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/226f4a490d1a938fc838d8f8c46a4eca864c0d78
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/5b0c4c916f202b8fd13d12afb6af62b385622f81
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/a8a7e6a9ff8a4c1f067694ddbd44be67fdf36693
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/d0a4dc7efa825bce60a8da8f7d43c864a159abde

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/xfrm/xfrm_nat_keepalive.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "d0a4dc7efa825bce60a8da8f7d43c864a159abde",
              "status": "affected",
              "version": "f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae",
              "versionType": "git"
            },
            {
              "lessThan": "5b0c4c916f202b8fd13d12afb6af62b385622f81",
              "status": "affected",
              "version": "f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae",
              "versionType": "git"
            },
            {
              "lessThan": "a8a7e6a9ff8a4c1f067694ddbd44be67fdf36693",
              "status": "affected",
              "version": "f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae",
              "versionType": "git"
            },
            {
              "lessThan": "226f4a490d1a938fc838d8f8c46a4eca864c0d78",
              "status": "affected",
              "version": "f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/xfrm/xfrm_nat_keepalive.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.11"
            },
            {
              "lessThan": "6.11",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.101",
              "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"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: nat_keepalive: avoid double free on send error\n\nnat_keepalive_send() frees the keepalive skb whenever the IPv4 or IPv6\nsend helper reports an error.\n\nThat cleanup is only correct before the skb is handed to the output\npath. Once ip_build_and_send_pkt() or ip6_xmit() takes ownership, the\nnetworking stack may already have consumed the skb before returning an\nerror, so freeing it again is unsafe.\n\nHandle the pre-handoff failure cases inside nat_keepalive_send_ipv4()\nand nat_keepalive_send_ipv6(), where the caller still owns the skb, and\nkeep nat_keepalive_send() responsible only for family dispatch and the\nunsupported-family cleanup path."
    }
  ],
  "id": "CVE-2026-72137",
  "lastModified": "2026-08-17T06:18:13.583",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-08-15T06:21:31.223",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/226f4a490d1a938fc838d8f8c46a4eca864c0d78"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/5b0c4c916f202b8fd13d12afb6af62b385622f81"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a8a7e6a9ff8a4c1f067694ddbd44be67fdf36693"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d0a4dc7efa825bce60a8da8f7d43c864a159abde"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}

CVE-2026-72137 (GCVE-0-2026-72137)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:53 – Updated: 2026-08-17 05:40

Title

xfrm: nat_keepalive: avoid double free on send error

Summary

Severity

9.8 (Critical)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Assigner

Linux mitre root

References

4 references

URL	Tags
https://git.kernel.org/stable/c/d0a4dc7efa825bce6…
https://git.kernel.org/stable/c/5b0c4c916f202b8fd…
https://git.kernel.org/stable/c/a8a7e6a9ff8a4c1f0…
https://git.kernel.org/stable/c/226f4a490d1a938fc…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae , < d0a4dc7efa825bce60a8da8f7d43c864a159abde (git) Affected: f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae , < 5b0c4c916f202b8fd13d12afb6af62b385622f81 (git) Affected: f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae , < a8a7e6a9ff8a4c1f067694ddbd44be67fdf36693 (git) Affected: f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae , < 226f4a490d1a938fc838d8f8c46a4eca864c0d78 (git)
Linux	Linux	Affected: 6.11 Unaffected: 0 , < 6.11 (semver) Unaffected: 6.12.101 , ≤ 6.12.* (semver) Unaffected: 6.18.40 , ≤ 6.18.* (semver) Unaffected: 7.1.5 , ≤ 7.1.* (semver) Unaffected: 7.2 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/xfrm/xfrm_nat_keepalive.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "d0a4dc7efa825bce60a8da8f7d43c864a159abde",
              "status": "affected",
              "version": "f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae",
              "versionType": "git"
            },
            {
              "lessThan": "5b0c4c916f202b8fd13d12afb6af62b385622f81",
              "status": "affected",
              "version": "f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae",
              "versionType": "git"
            },
            {
              "lessThan": "a8a7e6a9ff8a4c1f067694ddbd44be67fdf36693",
              "status": "affected",
              "version": "f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae",
              "versionType": "git"
            },
            {
              "lessThan": "226f4a490d1a938fc838d8f8c46a4eca864c0d78",
              "status": "affected",
              "version": "f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/xfrm/xfrm_nat_keepalive.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.11"
            },
            {
              "lessThan": "6.11",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.101",
              "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": "6.12.101",
                  "versionStartIncluding": "6.11",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.40",
                  "versionStartIncluding": "6.11",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.5",
                  "versionStartIncluding": "6.11",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2",
                  "versionStartIncluding": "6.11",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: nat_keepalive: avoid double free on send error\n\nnat_keepalive_send() frees the keepalive skb whenever the IPv4 or IPv6\nsend helper reports an error.\n\nThat cleanup is only correct before the skb is handed to the output\npath. Once ip_build_and_send_pkt() or ip6_xmit() takes ownership, the\nnetworking stack may already have consumed the skb before returning an\nerror, so freeing it again is unsafe.\n\nHandle the pre-handoff failure cases inside nat_keepalive_send_ipv4()\nand nat_keepalive_send_ipv6(), where the caller still owns the skb, and\nkeep nat_keepalive_send() responsible only for family dispatch and the\nunsupported-family cleanup path."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - On internet-facing IPsec VPN gateways using kernel NAT keepalive, a remote attacker can induce post-handoff outbound send failures (e.g., ENOMEM from network-driven memory pressure) when periodic keepalives are transmitted, reaching the vulnerable double-free path.\nAC:L - After an outbound ESP-in-UDP SA has NAT keepalive configured, an attacker can reliably force send errors where the stack already consumed the skb (ip6_xmit EMSGSIZE, ip_finish_output2 neighbour/ENOMEM paths) without uncontrollable races or memory layout dependencies.\nPR:N - Remote exploitation requires no privileges on the victim; it only needs a typical IPsec NAT-T deployment where userspace already set XFRMA_NAT_KEEPALIVE_INTERVAL. Local exploitation via user namespaces needs only CAP_NET_ADMIN (PR:L), not root in the init namespace.\nUI:N - No victim or administrator interaction is needed during exploitation; NAT keepalives are sent automatically by the kernel delayed work queue on the configured interval once the XFRM SA exists.\nS:U - Impact is kernel heap corruption and privilege escalation within the same security authority; this is not a VM escape, container breakout, or IOMMU/DMA boundary bypass.\nC:H - The skb double-free corrupts the slab allocator and yields use-after-free primitives that can be leveraged for arbitrary kernel memory disclosure, not merely a bounded leak or crash-only NULL dereference.\nI:H - Double-free heap corruption enables attacker-controlled reallocation of freed sk_buff objects, supporting arbitrary kernel memory writes, control-flow hijacking, and local privilege escalation.\nA:H - The double-free reliably causes slab corruption, kernel oops, or panic during keepalive send-error cleanup, providing immediate and repeatable denial of service on affected systems."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:40:47.767Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/d0a4dc7efa825bce60a8da8f7d43c864a159abde"
        },
        {
          "url": "https://git.kernel.org/stable/c/5b0c4c916f202b8fd13d12afb6af62b385622f81"
        },
        {
          "url": "https://git.kernel.org/stable/c/a8a7e6a9ff8a4c1f067694ddbd44be67fdf36693"
        },
        {
          "url": "https://git.kernel.org/stable/c/226f4a490d1a938fc838d8f8c46a4eca864c0d78"
        }
      ],
      "title": "xfrm: nat_keepalive: avoid double free on send error",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-72137",
    "datePublished": "2026-08-15T05:53:11.812Z",
    "dateReserved": "2026-08-09T03:40:39.908Z",
    "dateUpdated": "2026-08-17T05:40:47.767Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
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.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

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FKIE_CVE-2026-72137

CVE-2026-72137 (GCVE-0-2026-72137)

Tags

Sightings

Nomenclature