FKIE_CVE-2026-53267

Vulnerability from fkie_nvd - Published: 2026-06-25 09:16 - Updated: 2026-06-30 14:44
Severity
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_ct: bail out on template ct in get eval I noticed this issue while looking at a historic syzbot report [1]. A rule like the one below is enough to trigger the bug: table ip t { chain pre { type filter hook prerouting priority raw; ct zone set 1 ct original saddr 1.2.3.4 accept } } The first expression attaches a per-cpu template ct via nft_ct_set_zone_eval() (nf_ct_tmpl_alloc -> kzalloc, tuple is all zero, nf_ct_l3num(ct) == 0). The next expression then calls nft_ct_get_eval() on the same skb, treats the template as a real ct and hits the 16-byte memcpy path. With dreg at NFT_REG32_15 this overflows past struct nft_regs on the kernel stack; with smaller dreg values it silently clobbers adjacent registers. Reject template ct at the eval entry and in nft_ct_get_fast_eval(), mirroring the check nft_ct_set_eval() already has. Additionally, bound the address copy in NFT_CT_SRC / NFT_CT_DST by priv->len instead of by nf_ct_l3num(ct): nf_ct_get_tuple() zeroes the tuple before pkt_to_tuple() fills in only the protocol-relevant leading bytes, so the trailing bytes of tuple->{src,dst}.u3.all are well-defined zero. priv->len is validated at rule load, so the copy size is now bounded by the destination register rather than by an untrusted field on the conntrack. [1]: https://syzkaller.appspot.com/bug?id=389cf09cb72926114fce90dc85a2c3231dcb647c
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2e154b5f53f1b0b490c7b8b02499f90feb86b1d5
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/3027ecbdb5fdf9200251c21d4818e4c447ef78e1
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8470f676eadeab99132708acb1a85915664d6115
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/af80f78ce984649e1698b841cd33f4fa505ad828
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f071b0bf078146368d18e4eec386bf2ddc0ab7e0
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/netfilter/nft_ct.c",
            "net/netfilter/nft_ct_fast.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "af80f78ce984649e1698b841cd33f4fa505ad828",
              "status": "affected",
              "version": "45d9bcda21f4c13be75e3571b0f0ef39e77934b5",
              "versionType": "git"
            },
            {
              "lessThan": "8470f676eadeab99132708acb1a85915664d6115",
              "status": "affected",
              "version": "45d9bcda21f4c13be75e3571b0f0ef39e77934b5",
              "versionType": "git"
            },
            {
              "lessThan": "f071b0bf078146368d18e4eec386bf2ddc0ab7e0",
              "status": "affected",
              "version": "45d9bcda21f4c13be75e3571b0f0ef39e77934b5",
              "versionType": "git"
            },
            {
              "lessThan": "2e154b5f53f1b0b490c7b8b02499f90feb86b1d5",
              "status": "affected",
              "version": "45d9bcda21f4c13be75e3571b0f0ef39e77934b5",
              "versionType": "git"
            },
            {
              "lessThan": "3027ecbdb5fdf9200251c21d4818e4c447ef78e1",
              "status": "affected",
              "version": "45d9bcda21f4c13be75e3571b0f0ef39e77934b5",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/netfilter/nft_ct.c",
            "net/netfilter/nft_ct_fast.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.1"
            },
            {
              "lessThan": "4.1",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.143",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.94",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.36",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.13",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "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\nnetfilter: nft_ct: bail out on template ct in get eval\n\nI noticed this issue while looking at a historic syzbot report [1].\n\nA rule like the one below is enough to trigger the bug:\n\n    table ip t {\n        chain pre {\n            type filter hook prerouting priority raw;\n            ct zone set 1\n            ct original saddr 1.2.3.4 accept\n        }\n    }\n\nThe first expression attaches a per-cpu template ct via\nnft_ct_set_zone_eval() (nf_ct_tmpl_alloc -\u003e kzalloc, tuple is all\nzero, nf_ct_l3num(ct) == 0). The next expression then calls\nnft_ct_get_eval() on the same skb, treats the template as a real ct\nand hits the 16-byte memcpy path. With dreg at NFT_REG32_15 this\noverflows past struct nft_regs on the kernel stack; with smaller\ndreg values it silently clobbers adjacent registers.\n\nReject template ct at the eval entry and in nft_ct_get_fast_eval(),\nmirroring the check nft_ct_set_eval() already has. Additionally,\nbound the address copy in NFT_CT_SRC / NFT_CT_DST by priv-\u003elen\ninstead of by nf_ct_l3num(ct): nf_ct_get_tuple() zeroes the tuple\nbefore pkt_to_tuple() fills in only the protocol-relevant leading\nbytes, so the trailing bytes of tuple-\u003e{src,dst}.u3.all are\nwell-defined zero. priv-\u003elen is validated at rule load, so the\ncopy size is now bounded by the destination register rather than\nby an untrusted field on the conntrack.\n\n[1]: https://syzkaller.appspot.com/bug?id=389cf09cb72926114fce90dc85a2c3231dcb647c"
    }
  ],
  "id": "CVE-2026-53267",
  "lastModified": "2026-06-30T14:44:27.313",
  "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": "2026-06-25T09:16:44.770",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/2e154b5f53f1b0b490c7b8b02499f90feb86b1d5"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/3027ecbdb5fdf9200251c21d4818e4c447ef78e1"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8470f676eadeab99132708acb1a85915664d6115"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/af80f78ce984649e1698b841cd33f4fa505ad828"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f071b0bf078146368d18e4eec386bf2ddc0ab7e0"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}


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