ppp: fix race conditions in ppp_fill_forward_path

{
  "id": "e4dfba1e103fd8d3c035cff8c609ec78977ac7620bf3117b7e63935f74c6943a",
  "url": "https://osv.dev/vulnerability/CVE-2025-39673",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ppp: fix race conditions in ppp_fill_forward_path",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: ppp: fix race conditions in ppp_fill_forward_path ppp_fill_forward_path() has two race conditions: 1. The ppp->channels list can change between list_empty() and list_first_entry(), as ppp_lock() is not held. If the only channel is deleted in ppp_disconnect_channel(), list_first_entry() may access an empty head or a freed entry, and trigger a panic. 2. pch->chan can be NULL. When ppp_unregister_channel() is called, pch->chan is set to NULL before pch is removed from ppp->channels. Fix these by using a lockless RCU approach: - Use list_first_or_null_rcu() to safely test and access the first list entry. - Convert list modifications on ppp->channels to their RCU variants and add synchronize_net() after removal. - Check for a NULL pch->chan before dereferencing it.",
    "evidence": "osv:CVE-2025-39673",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
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            "value": "5.15.190",
            "evidence": "/affected/1/ranges"
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          {
            "value": "6.1.149",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.103",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.44",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.16.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "critical",
    "structured": {
      "id": "CVE-2025-39673",
      "aliases": [
        "CVE-2025-39673"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
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                  "fixed": "94731cc551e29511d85aa8dec61a6c071b1f2430"
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                {
                  "fixed": "f97f6475fdcb3c28ff3c55cc4b7bde632119ec08"
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                  "fixed": "0417adf367a0af11adf7ace849af4638cfb573f7"
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-39673.json"
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              "type": "ECOSYSTEM",
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          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-39673.json"
          }
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      ],
      "modified": "2026-10-28T02:30:50.439037785Z",
      "provider": "osv",
      "references": [
        "https://cert-portal.siemens.com/productcert/html/ssa-032379.html",
        "https://git.kernel.org/stable/c/0417adf367a0af11adf7ace849af4638cfb573f7",
        "https://git.kernel.org/stable/c/0f1630be6fcca3f0c63e4b242ad202e5cde28a40",
        "https://git.kernel.org/stable/c/94731cc551e29511d85aa8dec61a6c071b1f2430",
        "https://git.kernel.org/stable/c/9a1969fbffc1f1900d92d7594b1b7d8d72ef3dc7",
        "https://git.kernel.org/stable/c/ca18d751bcc9faf5b7e82e9fae1223d103928181",
        "https://git.kernel.org/stable/c/f97f6475fdcb3c28ff3c55cc4b7bde632119ec08",
        "https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39673.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-39673",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39673.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-39673",
        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 519035,
  "published_at": "2025-09-05T17:20:38.769+00:00"
}