FKIE_CVE-2026-43026

Vulnerability from fkie_nvd - Published: 2026-05-01 15:16 - Updated: 2026-06-17 10:48
Severity
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/1c2ebdeff8d088a2e47ae25d7b38447249adace2Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2898080c054ea4d6ddfaaf21bbedbc229a9a8376Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/35177c6877134a21315f37d57a5577846225623ePatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/929f7a9a7aad9404a5867216c3f8738232355b38Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a5a89db6981a1ddf2314bf50cb49db5a3146185fPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a64b7bf84b4d5ea54218c5d374ec87fff9000f43Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/bff0f4f06f12d6d9bc565a3e1378abd4f6f5ce36Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/fd002ff2ea030cbfb0188a11b3c60ce7f84485f4Patch
Impacted products
Vendor Product Version
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
To clipboard 

{
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    {
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          "product": "Linux",
          "programFiles": [
            "net/netfilter/nf_conntrack_netlink.c"
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          "vendor": "Linux",
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              "version": "3.4"
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              "version": "0",
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              "status": "unaffected",
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              "status": "unaffected",
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              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.22",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.19.*",
              "status": "unaffected",
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            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "configurations": [
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  ],
  "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."
    }
  ],
  "id": "CVE-2026-43026",
  "lastModified": "2026-06-17T10:48:47.427",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 5.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ]
  },
  "published": "2026-05-01T15:16:47.033",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
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      ],
      "url": "https://git.kernel.org/stable/c/1c2ebdeff8d088a2e47ae25d7b38447249adace2"
    },
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      "url": "https://git.kernel.org/stable/c/2898080c054ea4d6ddfaaf21bbedbc229a9a8376"
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    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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      "url": "https://git.kernel.org/stable/c/929f7a9a7aad9404a5867216c3f8738232355b38"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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      "url": "https://git.kernel.org/stable/c/a64b7bf84b4d5ea54218c5d374ec87fff9000f43"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
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      "url": "https://git.kernel.org/stable/c/bff0f4f06f12d6d9bc565a3e1378abd4f6f5ce36"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
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      "url": "https://git.kernel.org/stable/c/fd002ff2ea030cbfb0188a11b3c60ce7f84485f4"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "NVD-CWE-noinfo"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}


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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.
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