CVE-2026-43026 (GCVE-0-2026-43026)

Vulnerability from cvelistv5 – Published: 2026-05-01 14:15 – Updated: 2026-05-01 14:15
VLAI?
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.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 076a0ca02644657b13e4af363f487ced2942e9cb , < a5a89db6981a1ddf2314bf50cb49db5a3146185f (git)
Affected: 076a0ca02644657b13e4af363f487ced2942e9cb , < 1c2ebdeff8d088a2e47ae25d7b38447249adace2 (git)
Affected: 076a0ca02644657b13e4af363f487ced2942e9cb , < a64b7bf84b4d5ea54218c5d374ec87fff9000f43 (git)
Affected: 076a0ca02644657b13e4af363f487ced2942e9cb , < 2898080c054ea4d6ddfaaf21bbedbc229a9a8376 (git)
Affected: 076a0ca02644657b13e4af363f487ced2942e9cb , < fd002ff2ea030cbfb0188a11b3c60ce7f84485f4 (git)
Affected: 076a0ca02644657b13e4af363f487ced2942e9cb , < 929f7a9a7aad9404a5867216c3f8738232355b38 (git)
Affected: 076a0ca02644657b13e4af363f487ced2942e9cb , < bff0f4f06f12d6d9bc565a3e1378abd4f6f5ce36 (git)
Affected: 076a0ca02644657b13e4af363f487ced2942e9cb , < 35177c6877134a21315f37d57a5577846225623e (git)
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    Linux Linux Affected: 3.4
Unaffected: 0 , < 3.4 (semver)
Unaffected: 5.10.253 , ≤ 5.10.* (semver)
Unaffected: 5.15.203 , ≤ 5.15.* (semver)
Unaffected: 6.1.168 , ≤ 6.1.* (semver)
Unaffected: 6.6.134 , ≤ 6.6.* (semver)
Unaffected: 6.12.81 , ≤ 6.12.* (semver)
Unaffected: 6.18.22 , ≤ 6.18.* (semver)
Unaffected: 6.19.12 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/netfilter/nf_conntrack_netlink.c"
          ],
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              "versionType": "git"
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "3.4"
            },
            {
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "5.10.253",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.203",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.168",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
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              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
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              "versionType": "semver"
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            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.22",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.19.*",
              "status": "unaffected",
              "version": "6.19.12",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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                  "versionStartIncluding": "3.4",
                  "vulnerable": true
                },
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent\n\nctnetlink_alloc_expect() allocates expectations from a non-zeroing\nslab cache via nf_ct_expect_alloc().  When CTA_EXPECT_NAT is not\npresent in the netlink message, saved_addr and saved_proto are\nnever initialized.  Stale data from a previous slab occupant can\nthen be dumped to userspace by ctnetlink_exp_dump_expect(), which\nchecks these fields to decide whether to emit CTA_EXPECT_NAT.\n\nThe safe sibling nf_ct_expect_init(), used by the packet path,\nexplicitly zeroes these fields.\n\nZero saved_addr, saved_proto and dir in the else branch, guarded\nby IS_ENABLED(CONFIG_NF_NAT) since these fields only exist when\nNAT is enabled.\n\nConfirmed by priming the expect slab with NAT-bearing expectations,\nfreeing them, creating a new expectation without CTA_EXPECT_NAT,\nand observing that the ctnetlink dump emits a spurious\nCTA_EXPECT_NAT containing stale data from the prior allocation."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-01T14:15:27.854Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a5a89db6981a1ddf2314bf50cb49db5a3146185f"
        },
        {
          "url": "https://git.kernel.org/stable/c/1c2ebdeff8d088a2e47ae25d7b38447249adace2"
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          "url": "https://git.kernel.org/stable/c/a64b7bf84b4d5ea54218c5d374ec87fff9000f43"
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        },
        {
          "url": "https://git.kernel.org/stable/c/35177c6877134a21315f37d57a5577846225623e"
        }
      ],
      "title": "netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-43026",
    "datePublished": "2026-05-01T14:15:27.854Z",
    "dateReserved": "2026-05-01T14:12:55.976Z",
    "dateUpdated": "2026-05-01T14:15:27.854Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-43026",
      "date": "2026-05-07",
      "epss": "0.00032",
      "percentile": "0.09285"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-43026\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-05-01T15:16:47.033\",\"lastModified\":\"2026-05-01T15:24:14.893\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnetfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent\\n\\nctnetlink_alloc_expect() allocates expectations from a non-zeroing\\nslab cache via nf_ct_expect_alloc().  When CTA_EXPECT_NAT is not\\npresent in the netlink message, saved_addr and saved_proto are\\nnever initialized.  Stale data from a previous slab occupant can\\nthen be dumped to userspace by ctnetlink_exp_dump_expect(), which\\nchecks these fields to decide whether to emit CTA_EXPECT_NAT.\\n\\nThe safe sibling nf_ct_expect_init(), used by the packet path,\\nexplicitly zeroes these fields.\\n\\nZero saved_addr, saved_proto and dir in the else branch, guarded\\nby IS_ENABLED(CONFIG_NF_NAT) since these fields only exist when\\nNAT is enabled.\\n\\nConfirmed by priming the expect slab with NAT-bearing expectations,\\nfreeing them, creating a new expectation without CTA_EXPECT_NAT,\\nand observing that the ctnetlink dump emits a spurious\\nCTA_EXPECT_NAT containing stale data from the prior allocation.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/1c2ebdeff8d088a2e47ae25d7b38447249adace2\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/2898080c054ea4d6ddfaaf21bbedbc229a9a8376\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/35177c6877134a21315f37d57a5577846225623e\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/929f7a9a7aad9404a5867216c3f8738232355b38\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a5a89db6981a1ddf2314bf50cb49db5a3146185f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a64b7bf84b4d5ea54218c5d374ec87fff9000f43\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/bff0f4f06f12d6d9bc565a3e1378abd4f6f5ce36\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/fd002ff2ea030cbfb0188a11b3c60ce7f84485f4\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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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.

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  • 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.



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