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netfilter: xt_multiport: validate range encoding in checkentry

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: netfilter: xt_multiport: validate range encoding in checkentry ports_match_v1() treats any non-zero pflags entry as the start of a port range and unconditionally consumes the next ports[] element as the range end. The checkentry path currently validates protocol, flags and count, but it does not validate the range encoding itself. As a result, malformed rules can mark the last slot as a range start or place two range starts back to back, leaving ports_match_v1() to step past the last valid ports[] element while interpreting the rule. Reject malformed multiport v1 rules in checkentry by validating that each range start has a following element and that the following element is not itself marked as another range start.

Announced Group revision 1
Original source ↗

CVE-2026-31681

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-2026-31681

Linux

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

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

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": "a89ecb6a2ef732d04058d87801e2b6bd7e5c7089",
        "lessThan": "8c5bf8f5b478f569191c4a7982de7cd5f5f73c1a",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "a89ecb6a2ef732d04058d87801e2b6bd7e5c7089",
        "lessThan": "c9749f6232c845e31c21d4cc72200211df15d8a2",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "a89ecb6a2ef732d04058d87801e2b6bd7e5c7089",
        "lessThan": "b67d638cbee9975c765feb45c126e96ed11ec802",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "a89ecb6a2ef732d04058d87801e2b6bd7e5c7089",
        "lessThan": "36bf0d98e180a7c384c8d8a59b0d2d4b80e5eb16",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "a89ecb6a2ef732d04058d87801e2b6bd7e5c7089",
        "lessThan": "aec14808271f2bf2b656de6ff12dfe73c5fd3b67",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "a89ecb6a2ef732d04058d87801e2b6bd7e5c7089",
        "lessThan": "8368ce8eb01f0b91111d814703696e780d0ef12f",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "a89ecb6a2ef732d04058d87801e2b6bd7e5c7089",
        "lessThan": "1e4baa853f1cc4227e04f52d6860524707cfb294",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "a89ecb6a2ef732d04058d87801e2b6bd7e5c7089",
        "lessThan": "ff64c5bfef12461df8450e0f50bb693b5269c720",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "net/netfilter/xt_multiport.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "2.6.17"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "2.6.17",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "5.10.258",
        "versionType": "semver",
        "lessThanOrEqual": "5.10.*"
      },
      {
        "status": "unaffected",
        "version": "5.15.209",
        "versionType": "semver",
        "lessThanOrEqual": "5.15.*"
      },
      {
        "status": "unaffected",
        "version": "6.1.175",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.136",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.83",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.24",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "6.19.14",
        "versionType": "semver",
        "lessThanOrEqual": "6.19.*"
      },
      {
        "status": "unaffected",
        "version": "7.0",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "net/netfilter/xt_multiport.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-31681

Source reference: /cveMetadata/cveId

Publisher severity

No explicit severity was provided.

Event
#28312 · Revision 1
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Publisher date
Read the original announcement

Revision history

  1. CVE-2026-31681 · Revision 1Source updated