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pppoe: drop PFC frames

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: pppoe: drop PFC frames RFC 2516 Section 7 states that Protocol Field Compression (PFC) is NOT RECOMMENDED for PPPoE. In practice, pppd does not support negotiating PFC for PPPoE sessions, and the current PPPoE driver assumes an uncompressed (2-byte) protocol field. However, the generic PPP layer function ppp_input() is not aware of the negotiation result, and still accepts PFC frames. If a peer with a broken implementation or an attacker sends a frame with a compressed (1-byte) protocol field, the subsequent PPP payload is shifted by one byte. This causes the network header to be 4-byte misaligned, which may trigger unaligned access exceptions on some architectures. To reduce the attack surface, drop PPPoE PFC frames. Introduce ppp_skb_is_compressed_proto() helper function to be used in both ppp_generic.c and pppoe.c to avoid open-coding.

Announced Source revision 1
Original source ↗

CVE-2026-53003

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-2026-53003

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": "7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6",
        "lessThan": "cb3beef35ab5e0c1afca9fd7648c6ae499786377",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6",
        "lessThan": "ba758fdf1399f310b30098b6faa3fd043de47dd2",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6",
        "lessThan": "fcca1df05322bb04e344dd1178b54b76a08eb7c3",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6",
        "lessThan": "8a5e840babc5c0fbd10c73728a13192347771ec6",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6",
        "lessThan": "49e41b60ccd1bdbe9e218420f716dd5f9a2f9c71",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6",
        "lessThan": "0cab5d077dd1efd2bd1a47271acc35894f945b4f",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6",
        "lessThan": "2b5c3c040d020e3ab3b9a8887031202d96843b1e",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6",
        "lessThan": "cc1ff87bce1ccd38410ab10960f576dcd17db679",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "drivers/net/ppp/ppp_generic.c",
      "drivers/net/ppp/pppoe.c",
      "include/linux/ppp_defs.h"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "5.0"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "5.0",
        "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": "6.6.141",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.91",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.33",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "7.0.10",
        "versionType": "semver",
        "lessThanOrEqual": "7.0.*"
      },
      {
        "status": "unaffected",
        "version": "7.1",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "drivers/net/ppp/ppp_generic.c",
      "drivers/net/ppp/pppoe.c",
      "include/linux/ppp_defs.h"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-53003

Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event
#40731 · Revision 1
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Publisher date
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