GHSA-4PWV-PMM4-FW4R

Vulnerability from github – Published: 2026-07-27 09:31 – Updated: 2026-07-28 12:31
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

net: openvswitch: reject oversized nested action attrs

Open vSwitch stores generated flow actions as nlattrs, whose nla_len field is u16. Commit a1e64addf3ff ("net: openvswitch: remove misbehaving actions length check") allowed the total sw_flow_actions stream to grow beyond 64 KiB, which is valid, but also removed the last guard preventing a generated nested action attribute from exceeding U16_MAX.

An oversized generated container can thus be closed with a truncated nla_len. A later dump or teardown then walks a structurally different stream than the one that was validated. In particular, an oversized nested CLONE/CT action may cause subsequent bytes in the generated stream to be interpreted as independent actions.

Keep the larger total-action-stream behavior, but make nested action close reject generated containers that do not fit in nla_len, and return the error through all callers. For recursive SAMPLE, CLONE, DEC_TTL, and CHECK_PKT_LEN builders, trim resource-owning action-list tails in reverse construction order before discarding failed wrappers, so resources copied into the rejected tails are released before the wrappers are removed.

Most failed outer wrappers are discarded by truncating actions_len after child resources have been released. CHECK_PKT_LEN also trims its parent after branch resources are gone. SET/TUNNEL close failures unwind their known tun_dst ownership directly, and SET_TO_MASKED has no external ownership and truncates on close failure.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-64531"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-27T08:16:22Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: openvswitch: reject oversized nested action attrs\n\nOpen vSwitch stores generated flow actions as nlattrs, whose nla_len\nfield is u16. Commit a1e64addf3ff (\"net: openvswitch: remove\nmisbehaving actions length check\") allowed the total sw_flow_actions\nstream to grow beyond 64 KiB, which is valid, but also removed the last\nguard preventing a generated nested action attribute from exceeding\nU16_MAX.\n\nAn oversized generated container can thus be closed with a truncated\nnla_len. A later dump or teardown then walks a structurally different\nstream than the one that was validated. In particular, an oversized\nnested CLONE/CT action may cause subsequent bytes in the generated\nstream to be interpreted as independent actions.\n\nKeep the larger total-action-stream behavior, but make nested action\nclose reject generated containers that do not fit in nla_len, and return\nthe error through all callers. For recursive SAMPLE, CLONE, DEC_TTL, and\nCHECK_PKT_LEN builders, trim resource-owning action-list tails in reverse\nconstruction order before discarding failed wrappers, so resources copied\ninto the rejected tails are released before the wrappers are removed.\n\nMost failed outer wrappers are discarded by truncating actions_len after\nchild resources have been released. CHECK_PKT_LEN also trims its parent\nafter branch resources are gone. SET/TUNNEL close failures unwind their\nknown tun_dst ownership directly, and SET_TO_MASKED has no external\nownership and truncates on close failure.",
  "id": "GHSA-4pwv-pmm4-fw4r",
  "modified": "2026-07-28T12:31:19Z",
  "published": "2026-07-27T09:31:26Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64531"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1b41cbe05b184f8861712f0806cc0c4f5d8c6dfe"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3f1f755366687d051174739fb99f7d560202f60b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ab855641241387db062a5e41d9ad6b8561542572"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c66bd2626c2764f23764ff0f8277f44a9cfe8349"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d573250d228401f707f4dbc09d11227a6215ee5f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/dbd14f736be02cfe73049bd801af89becd1a0749"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f1efff8858403191361a01269c6fe8dd7f55a385"
    },
    {
      "type": "WEB",
      "url": "http://www.openwall.com/lists/oss-security/2026/07/28/8"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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