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tcp: exclude old ACKs from tcp fast path

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: tcp: exclude old ACKs from tcp fast path Exclude old ACKs before SND.UNA from the tcp fast path as well as ACKs after SND.NXT. Such ACKs will fall through to the slow path, where tcp_ack() performs the appropriate validation and challenge ACK handling according to RFC5961 and Commit 3d501dd326fb1c7 ("tcp: do not accept ACK of bytes we never sent"). This prevents old ACKs from being accepted or modifying connection state as part of the fast path before appropriate ACK validation is applied. In particular, this prevents payload carried by a segment with an excessively old ACK from advancing RCV.NXT before the ACK is rejected.

Announced Source revision 1
Original source ↗

CVE-2026-98255

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-2026-98255

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": "31770e34e43d6c8dee129bfee77e56c34e61f0e5",
        "lessThan": "07cacab90290f795bad2e566790f4ba8e84cdf5f",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "31770e34e43d6c8dee129bfee77e56c34e61f0e5",
        "lessThan": "6eb9b697f50b73b9684e466c1e97f4ca8e947a59",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "31770e34e43d6c8dee129bfee77e56c34e61f0e5",
        "lessThan": "b86e1e5a4bbcbbccde8b7a3d3486604b581f6628",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "31770e34e43d6c8dee129bfee77e56c34e61f0e5",
        "lessThan": "1c8448db5cf35a13d82b0c9004ffdb49358883e7",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "31770e34e43d6c8dee129bfee77e56c34e61f0e5",
        "lessThan": "8309dc2cc360056aa9cd2acfbfc25930798c3b66",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "31770e34e43d6c8dee129bfee77e56c34e61f0e5",
        "lessThan": "ff037920c688ae6ca1153fec01e90e6782712455",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "31770e34e43d6c8dee129bfee77e56c34e61f0e5",
        "lessThan": "8205ac5ddb42a1843fa8d6a8c295b5c7f4f8c6ed",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "31770e34e43d6c8dee129bfee77e56c34e61f0e5",
        "lessThan": "f81e6c3fb06327bc49cdd6e559845293ba06a704",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "net/ipv4/tcp_input.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "4.14"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "4.14",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "5.10.271",
        "versionType": "semver",
        "lessThanOrEqual": "5.10.*"
      },
      {
        "status": "unaffected",
        "version": "5.15.222",
        "versionType": "semver",
        "lessThanOrEqual": "5.15.*"
      },
      {
        "status": "unaffected",
        "version": "6.1.189",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.158",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.112",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.54",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "7.2.8",
        "versionType": "semver",
        "lessThanOrEqual": "7.2.*"
      },
      {
        "status": "unaffected",
        "version": "7.3",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "net/ipv4/tcp_input.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-98255

Source reference: /cveMetadata/cveId

Publisher severity

No explicit severity was provided.

Event
#38334 · Revision 1
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Publisher date
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