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netfilter: nft_ct: bail out on template ct in get eval

Type: advisorySource: Official CVE List1 source record

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

Announced Source revision 1
Original source ↗

CVE-2026-53267

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-53267

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
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Fixed versions
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Prerequisites
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Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "45d9bcda21f4c13be75e3571b0f0ef39e77934b5",
        "lessThan": "af80f78ce984649e1698b841cd33f4fa505ad828",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "45d9bcda21f4c13be75e3571b0f0ef39e77934b5",
        "lessThan": "8470f676eadeab99132708acb1a85915664d6115",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "45d9bcda21f4c13be75e3571b0f0ef39e77934b5",
        "lessThan": "f071b0bf078146368d18e4eec386bf2ddc0ab7e0",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "45d9bcda21f4c13be75e3571b0f0ef39e77934b5",
        "lessThan": "2e154b5f53f1b0b490c7b8b02499f90feb86b1d5",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "45d9bcda21f4c13be75e3571b0f0ef39e77934b5",
        "lessThan": "3027ecbdb5fdf9200251c21d4818e4c447ef78e1",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "net/netfilter/nft_ct.c",
      "net/netfilter/nft_ct_fast.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "4.1"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "4.1",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "6.6.143",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.94",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.36",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "7.0.13",
        "versionType": "semver",
        "lessThanOrEqual": "7.0.*"
      },
      {
        "status": "unaffected",
        "version": "7.1",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "net/netfilter/nft_ct.c",
      "net/netfilter/nft_ct_fast.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-53267

Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event
#40799 · Revision 1
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