CVE-2026-43116 (GCVE-0-2026-43116)

Vulnerability from cvelistv5 – Published: 2026-05-06 07:40 – Updated: 2026-09-08 08:48
VLAI
Title
netfilter: ctnetlink: ensure safe access to master conntrack
Summary
In the Linux kernel, the following vulnerability has been resolved: netfilter: ctnetlink: ensure safe access to master conntrack Holding reference on the expectation is not sufficient, the master conntrack object can just go away, making exp->master invalid. To access exp->master safely: - Grab the nf_conntrack_expect_lock, this gets serialized with clean_from_lists() which also holds this lock when the master conntrack goes away. - Hold reference on master conntrack via nf_conntrack_find_get(). Not so easy since the master tuple to look up for the master conntrack is not available in the existing problematic paths. This patch goes for extending the nf_conntrack_expect_lock section to address this issue for simplicity, in the cases that are described below this is just slightly extending the lock section. The add expectation command already holds a reference to the master conntrack from ctnetlink_create_expect(). However, the delete expectation command needs to grab the spinlock before looking up for the expectation. Expand the existing spinlock section to address this to cover the expectation lookup. Note that, the nf_ct_expect_iterate_net() calls already grabs the spinlock while iterating over the expectation table, which is correct. The get expectation command needs to grab the spinlock to ensure master conntrack does not go away. This also expands the existing spinlock section to cover the expectation lookup too. I needed to move the netlink skb allocation out of the spinlock to keep it GFP_KERNEL. For the expectation events, the IPEXP_DESTROY event is already delivered under the spinlock, just move the delivery of IPEXP_NEW under the spinlock too because the master conntrack event cache is reached through exp->master. While at it, add lockdep notations to help identify what codepaths need to grab the spinlock.
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: c1d10adb4a521de5760112853f42aaeefcec96eb , < 9e1196d27ef496f404c76f7a9d03761142d991c4 (git)
Affected: c1d10adb4a521de5760112853f42aaeefcec96eb , < 5e1c1d22268ae710c238342c8030c21daf298168 (git)
Affected: c1d10adb4a521de5760112853f42aaeefcec96eb , < d52fa1fa7440676b8c238037a050ab008c22737f (git)
Affected: c1d10adb4a521de5760112853f42aaeefcec96eb , < f338ced0473849c9f6ed0b77ca99f1aab5826787 (git)
Affected: c1d10adb4a521de5760112853f42aaeefcec96eb , < 497f99b26fffdc5635706d1b4811f1ed8ee21a5b (git)
Affected: c1d10adb4a521de5760112853f42aaeefcec96eb , < bffcaad9afdfe45d7fc777397d3b83c1e3ebffe5 (git)
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Linux Linux Affected: 2.6.16
Unaffected: 0 , < 2.6.16 (semver)
Unaffected: 6.1.176 , ≤ 6.1.* (semver)
Unaffected: 6.6.143 , ≤ 6.6.* (semver)
Unaffected: 6.12.94 , ≤ 6.12.* (semver)
Unaffected: 6.18.24 , ≤ 6.18.* (semver)
Unaffected: 6.19.14 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
guessed Create a notification for this product.
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
guessed Create a notification for this product.
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
guessed Create a notification for this product.
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                    "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*",
                    "matchCriteriaId": "4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*",
                    "matchCriteriaId": "F666C8D8-6538-46D4-B318-87610DE64C34",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*",
                    "matchCriteriaId": "02259FDA-961B-47BC-AE7F-93D7EC6E90C2",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*",
                    "matchCriteriaId": "58A9FEFF-C040-420D-8F0A-BFDAAA1DF258",
                    "vulnerable": true
                  }
                ],
                "negate": false,
                "operator": "OR"
              }
            ]
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: ctnetlink: ensure safe access to master conntrack\n\nHolding reference on the expectation is not sufficient, the master\nconntrack object can just go away, making exp-\u003emaster invalid.\n\nTo access exp-\u003emaster safely:\n\n- Grab the nf_conntrack_expect_lock, this gets serialized with\n  clean_from_lists() which also holds this lock when the master\n  conntrack goes away.\n\n- Hold reference on master conntrack via nf_conntrack_find_get().\n  Not so easy since the master tuple to look up for the master conntrack\n  is not available in the existing problematic paths.\n\nThis patch goes for extending the nf_conntrack_expect_lock section\nto address this issue for simplicity, in the cases that are described\nbelow this is just slightly extending the lock section.\n\nThe add expectation command already holds a reference to the master\nconntrack from ctnetlink_create_expect().\n\nHowever, the delete expectation command needs to grab the spinlock\nbefore looking up for the expectation. Expand the existing spinlock\nsection to address this to cover the expectation lookup. Note that,\nthe nf_ct_expect_iterate_net() calls already grabs the spinlock while\niterating over the expectation table, which is correct.\n\nThe get expectation command needs to grab the spinlock to ensure master\nconntrack does not go away. This also expands the existing spinlock\nsection to cover the expectation lookup too. I needed to move the\nnetlink skb allocation out of the spinlock to keep it GFP_KERNEL.\n\nFor the expectation events, the IPEXP_DESTROY event is already delivered\nunder the spinlock, just move the delivery of IPEXP_NEW under the\nspinlock too because the master conntrack event cache is reached through\nexp-\u003emaster.\n\nWhile at it, add lockdep notations to help identify what codepaths need\nto grab the spinlock."
          }
        ],
        "id": "CVE-2026-43116",
        "lastModified": "2026-09-08T09:18:03.600",
        "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"
            }
          ]
        },
        "published": "2026-05-06T10:16:25.400",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/497f99b26fffdc5635706d1b4811f1ed8ee21a5b"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/5e1c1d22268ae710c238342c8030c21daf298168"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/9e1196d27ef496f404c76f7a9d03761142d991c4"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/bffcaad9afdfe45d7fc777397d3b83c1e3ebffe5"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/d52fa1fa7440676b8c238037a050ab008c22737f"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/f338ced0473849c9f6ed0b77ca99f1aab5826787"
          },
          {
            "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e",
            "url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Modified",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-362"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-09-03T20:07:44+00:00",
      "cve": "CVE-2026-43116",
      "id": "CVE-2026-43116",
      "initial_release_date": "2026-05-06T00:00:00+00:00",
      "product_status:fixed": "2085",
      "product_status:known_affected": "36",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: netfilter: ctnetlink: ensure safe access to master conntrack",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-43116.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-10-03T00:55:32Z",
      "cve": "CVE-2026-43116",
      "id": "CVE-2026-43116",
      "initial_release_date": "2026-05-07T02:18:06Z",
      "product_status:known_affected": "697",
      "product_status:recommended": "393",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-43116",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-43116.json",
      "version": "13"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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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.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.