Skip to content
Heist/ feed
Back to feed
UnratedFix available

netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent

Type: advisorySources: OSV

In the Linux kernel, the following vulnerability has been resolved: netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent ctnetlink_alloc_expect() allocates expectations from a non-zeroing slab cache via nf_ct_expect_alloc(). When CTA_EXPECT_NAT is not present in the netlink message, saved_addr and saved_proto are never initialized. Stale data from a previous slab occupant can then be dumped to userspace by ctnetlink_exp_dump_expect(), which checks these fields to decide whether to emit CTA_EXPECT_NAT. The safe sibling nf_ct_expect_init(), used by the packet path, explicitly zeroes these fields. Zero saved_addr, saved_proto and dir in the else branch, guarded by IS_ENABLED(CONFIG_NF_NAT) since these fields only exist when NAT is enabled. Confirmed by priming the expect slab with NAT-bearing expectations, freeing them, creating a new expectation without CTA_EXPECT_NAT, and observing that the ctnetlink dump emits a spurious CTA_EXPECT_NAT containing stale data from the prior allocation.

Products
Kernel
Affected versions
Not specified
Fixed versions
5.10.253, 5.15.203, 6.1.168, 6.12.81, 6.18.22, 6.19.12, 6.6.134
CVEs
CVE-2026-43026
Confirmed fixed CVEs
Not specified
Updated in this feed
3 Nov 2026, 12:47 UTC · Revision 1

Source evidence

netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent

core-osv · Original source

Published 1 May 2026, 14:15 UTC

In the Linux kernel, the following vulnerability has been resolved: netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent ctnetlink_alloc_expect() allocates expectations from a non-zeroing slab cache via nf_ct_expect_alloc(). When CTA_EXPECT_NAT is not present in the netlink message, saved_addr and saved_proto are never initialized. Stale data from a previous slab occupant can then be dumped to userspace by ctnetlink_exp_dump_expect(), which checks these fields to decide whether to emit CTA_EXPECT_NAT. The safe sibling nf_ct_expect_init(), used by the packet path, explicitly zeroes these fields. Zero saved_addr, saved_proto and dir in the else branch, guarded by IS_ENABLED(CONFIG_NF_NAT) since these fields only exist when NAT is enabled. Confirmed by priming the expect slab with NAT-bearing expectations, freeing them, creating a new expectation without CTA_EXPECT_NAT, and observing that the ctnetlink dump emits a spurious CTA_EXPECT_NAT containing stale data from the prior allocation.

osv:CVE-2026-43026

Kernel

Fixed versions: 5.10.253, 5.15.203, 6.1.168, 6.6.134, 6.12.81, 6.18.22, 6.19.12

Complete source record
{
  "id": "1bd5d748b092a11dd508d0c5c3fca8fa69bfb2e556b78bfb0909c1d36ffdb018",
  "url": "https://osv.dev/vulnerability/CVE-2026-43026",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent ctnetlink_alloc_expect() allocates expectations from a non-zeroing slab cache via nf_ct_expect_alloc(). When CTA_EXPECT_NAT is not present in the netlink message, saved_addr and saved_proto are never initialized. Stale data from a previous slab occupant can then be dumped to userspace by ctnetlink_exp_dump_expect(), which checks these fields to decide whether to emit CTA_EXPECT_NAT. The safe sibling nf_ct_expect_init(), used by the packet path, explicitly zeroes these fields. Zero saved_addr, saved_proto and dir in the else branch, guarded by IS_ENABLED(CONFIG_NF_NAT) since these fields only exist when NAT is enabled. Confirmed by priming the expect slab with NAT-bearing expectations, freeing them, creating a new expectation without CTA_EXPECT_NAT, and observing that the ctnetlink dump emits a spurious CTA_EXPECT_NAT containing stale data from the prior allocation.",
    "evidence": "osv:CVE-2026-43026",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.10.253",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.15.203",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.168",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.134",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.81",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.22",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.19.12",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-43026",
      "aliases": [
        "CVE-2026-43026"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "076a0ca02644657b13e4af363f487ced2942e9cb"
                },
                {
                  "fixed": "a5a89db6981a1ddf2314bf50cb49db5a3146185f"
                },
                {
                  "fixed": "1c2ebdeff8d088a2e47ae25d7b38447249adace2"
                },
                {
                  "fixed": "a64b7bf84b4d5ea54218c5d374ec87fff9000f43"
                },
                {
                  "fixed": "2898080c054ea4d6ddfaaf21bbedbc229a9a8376"
                },
                {
                  "fixed": "fd002ff2ea030cbfb0188a11b3c60ce7f84485f4"
                },
                {
                  "fixed": "929f7a9a7aad9404a5867216c3f8738232355b38"
                },
                {
                  "fixed": "bff0f4f06f12d6d9bc565a3e1378abd4f6f5ce36"
                },
                {
                  "fixed": "35177c6877134a21315f37d57a5577846225623e"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43026.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "3.4.0"
                },
                {
                  "fixed": "5.10.253"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.11.0"
                },
                {
                  "fixed": "5.15.203"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.16.0"
                },
                {
                  "fixed": "6.1.168"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.6.134"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.81"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.22"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "6.19.12"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43026.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:28.976905143Z",
      "provider": "osv",
      "references": [
        "https://cert-portal.siemens.com/productcert/html/ssa-019113.html",
        "https://cert-portal.siemens.com/productcert/html/ssa-082556.html",
        "https://cert-portal.siemens.com/productcert/html/ssa-457936.html",
        "https://git.kernel.org/stable/c/1c2ebdeff8d088a2e47ae25d7b38447249adace2",
        "https://git.kernel.org/stable/c/2898080c054ea4d6ddfaaf21bbedbc229a9a8376",
        "https://git.kernel.org/stable/c/35177c6877134a21315f37d57a5577846225623e",
        "https://git.kernel.org/stable/c/929f7a9a7aad9404a5867216c3f8738232355b38",
        "https://git.kernel.org/stable/c/a5a89db6981a1ddf2314bf50cb49db5a3146185f",
        "https://git.kernel.org/stable/c/a64b7bf84b4d5ea54218c5d374ec87fff9000f43",
        "https://git.kernel.org/stable/c/bff0f4f06f12d6d9bc565a3e1378abd4f6f5ce36",
        "https://git.kernel.org/stable/c/fd002ff2ea030cbfb0188a11b3c60ce7f84485f4",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43026.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-43026",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43026.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-43026",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 495568,
  "published_at": "2026-05-01T14:15:27.854+00:00"
}