Vulnerability-Lookup

GHSA-QCF5-MJ4W-X99V

Vulnerability from github – Published: 2026-05-27 15:33 – Updated: 2026-05-27 15:33

Details

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

net: bridge: use a stable FDB dst snapshot in RCU readers

Local FDB entries can be rewritten in place by fdb_delete_local(), which updates f->dst to another port or to NULL while keeping the entry alive. Several bridge RCU readers inspect f->dst, including br_fdb_fillbuf() through the brforward_read() sysfs path.

These readers currently load f->dst multiple times and can therefore observe inconsistent values across the check and later dereference. In br_fdb_fillbuf(), this means a concurrent local-FDB update can change f->dst after the NULL check and before the port_no dereference, leading to a NULL-ptr-deref.

Fix this by taking a single READ_ONCE() snapshot of f->dst in each affected RCU reader and using that snapshot for the rest of the access sequence. Also publish the in-place f->dst updates in fdb_delete_local() with WRITE_ONCE() so the readers and writer use matching access patterns.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-46086"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-05-27T14:17:30Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: bridge: use a stable FDB dst snapshot in RCU readers\n\nLocal FDB entries can be rewritten in place by `fdb_delete_local()`, which\nupdates `f-\u003edst` to another port or to `NULL` while keeping the entry\nalive. Several bridge RCU readers inspect `f-\u003edst`, including\n`br_fdb_fillbuf()` through the `brforward_read()` sysfs path.\n\nThese readers currently load `f-\u003edst` multiple times and can therefore\nobserve inconsistent values across the check and later dereference.\nIn `br_fdb_fillbuf()`, this means a concurrent local-FDB update can change\n`f-\u003edst` after the NULL check and before the `port_no` dereference,\nleading to a NULL-ptr-deref.\n\nFix this by taking a single `READ_ONCE()` snapshot of `f-\u003edst` in each\naffected RCU reader and using that snapshot for the rest of the access\nsequence. Also publish the in-place `f-\u003edst` updates in `fdb_delete_local()`\nwith `WRITE_ONCE()` so the readers and writer use matching access patterns.",
  "id": "GHSA-qcf5-mj4w-x99v",
  "modified": "2026-05-27T15:33:23Z",
  "published": "2026-05-27T15:33:23Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-46086"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0b9e4bbfb7c949151e3acd44ed4aa33614d2e110"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5424e678f9b304e148cf5dcc047cffc7a56a3bb5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/81af4137a30c4c2dc694dea8cacb180bd66000ef"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9a2d9d4e657b23dc21f24cf139e3aeff0b61341f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/df4601653201de21b487c3e7fffd464790cab808"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-46086 (GCVE-0-2026-46086)

Vulnerability from cvelistv5 – Published: 2026-05-27 12:58 – Updated: 2026-05-27 12:58

Title

net: bridge: use a stable FDB dst snapshot in RCU readers

Summary

In the Linux kernel, the following vulnerability has been resolved: net: bridge: use a stable FDB dst snapshot in RCU readers Local FDB entries can be rewritten in place by `fdb_delete_local()`, which updates `f->dst` to another port or to `NULL` while keeping the entry alive. Several bridge RCU readers inspect `f->dst`, including `br_fdb_fillbuf()` through the `brforward_read()` sysfs path. These readers currently load `f->dst` multiple times and can therefore observe inconsistent values across the check and later dereference. In `br_fdb_fillbuf()`, this means a concurrent local-FDB update can change `f->dst` after the NULL check and before the `port_no` dereference, leading to a NULL-ptr-deref. Fix this by taking a single `READ_ONCE()` snapshot of `f->dst` in each affected RCU reader and using that snapshot for the rest of the access sequence. Also publish the in-place `f->dst` updates in `fdb_delete_local()` with `WRITE_ONCE()` so the readers and writer use matching access patterns.

Severity

No CVSS data available.

Assigner

Linux

References

5 references

URL	Tags
https://git.kernel.org/stable/c/0b9e4bbfb7c949151…
https://git.kernel.org/stable/c/81af4137a30c4c2dc…
https://git.kernel.org/stable/c/5424e678f9b304e14…
https://git.kernel.org/stable/c/9a2d9d4e657b23dc2…
https://git.kernel.org/stable/c/df4601653201de21b…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 960b589f86c74ce582922fcb996103271081f4de , < 0b9e4bbfb7c949151e3acd44ed4aa33614d2e110 (git) Affected: 960b589f86c74ce582922fcb996103271081f4de , < 81af4137a30c4c2dc694dea8cacb180bd66000ef (git) Affected: 960b589f86c74ce582922fcb996103271081f4de , < 5424e678f9b304e148cf5dcc047cffc7a56a3bb5 (git) Affected: 960b589f86c74ce582922fcb996103271081f4de , < 9a2d9d4e657b23dc21f24cf139e3aeff0b61341f (git) Affected: 960b589f86c74ce582922fcb996103271081f4de , < df4601653201de21b487c3e7fffd464790cab808 (git)
Linux	Linux	Affected: 3.14 Unaffected: 0 , < 3.14 (semver) Unaffected: 6.6.140 , ≤ 6.6.* (semver) Unaffected: 6.12.86 , ≤ 6.12.* (semver) Unaffected: 6.18.27 , ≤ 6.18.* (semver) Unaffected: 7.0.4 , ≤ 7.0.* (semver) Unaffected: 7.1-rc1 , ≤ * (original_commit_for_fix)

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{
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      "affected": [
        {
          "defaultStatus": "unaffected",
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            "net/bridge/br_arp_nd_proxy.c",
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              "status": "unaffected",
              "version": "6.18.27",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
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        },
        {
          "url": "https://git.kernel.org/stable/c/df4601653201de21b487c3e7fffd464790cab808"
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      "title": "net: bridge: use a stable FDB dst snapshot in RCU readers",
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    "datePublished": "2026-05-27T12:58:28.137Z",
    "dateReserved": "2026-05-13T15:03:33.096Z",
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}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

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GHSA-QCF5-MJ4W-X99V

CVE-2026-46086 (GCVE-0-2026-46086)

Tags

Sightings

Nomenclature