FKIE_CVE-2026-46086

Vulnerability from fkie_nvd - Published: 2026-05-27 14:17 - Updated: 2026-06-19 13:16
Severity
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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/0b9e4bbfb7c949151e3acd44ed4aa33614d2e110
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/1406c4e0ed1eaf8a29801ab1163d00fb7ee4359a
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/5424e678f9b304e148cf5dcc047cffc7a56a3bb5
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/81af4137a30c4c2dc694dea8cacb180bd66000ef
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9a2d9d4e657b23dc21f24cf139e3aeff0b61341f
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a6ae4511c07b91f597e461406c6330f0d4ff810e
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c502fa9f094cb03d1d1685c71e2105ab359bc2b8
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/df4601653201de21b487c3e7fffd464790cab808
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/bridge/br_arp_nd_proxy.c",
            "net/bridge/br_fdb.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "c502fa9f094cb03d1d1685c71e2105ab359bc2b8",
              "status": "affected",
              "version": "960b589f86c74ce582922fcb996103271081f4de",
              "versionType": "git"
            },
            {
              "lessThan": "a6ae4511c07b91f597e461406c6330f0d4ff810e",
              "status": "affected",
              "version": "960b589f86c74ce582922fcb996103271081f4de",
              "versionType": "git"
            },
            {
              "lessThan": "1406c4e0ed1eaf8a29801ab1163d00fb7ee4359a",
              "status": "affected",
              "version": "960b589f86c74ce582922fcb996103271081f4de",
              "versionType": "git"
            },
            {
              "lessThan": "0b9e4bbfb7c949151e3acd44ed4aa33614d2e110",
              "status": "affected",
              "version": "960b589f86c74ce582922fcb996103271081f4de",
              "versionType": "git"
            },
            {
              "lessThan": "81af4137a30c4c2dc694dea8cacb180bd66000ef",
              "status": "affected",
              "version": "960b589f86c74ce582922fcb996103271081f4de",
              "versionType": "git"
            },
            {
              "lessThan": "5424e678f9b304e148cf5dcc047cffc7a56a3bb5",
              "status": "affected",
              "version": "960b589f86c74ce582922fcb996103271081f4de",
              "versionType": "git"
            },
            {
              "lessThan": "9a2d9d4e657b23dc21f24cf139e3aeff0b61341f",
              "status": "affected",
              "version": "960b589f86c74ce582922fcb996103271081f4de",
              "versionType": "git"
            },
            {
              "lessThan": "df4601653201de21b487c3e7fffd464790cab808",
              "status": "affected",
              "version": "960b589f86c74ce582922fcb996103271081f4de",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/bridge/br_arp_nd_proxy.c",
            "net/bridge/br_fdb.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "3.14"
            },
            {
              "lessThan": "3.14",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.259",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.210",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.176",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.140",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.86",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "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",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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": "CVE-2026-46086",
  "lastModified": "2026-06-19T13:16:33.153",
  "metrics": {},
  "published": "2026-05-27T14:17:30.080",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/0b9e4bbfb7c949151e3acd44ed4aa33614d2e110"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/1406c4e0ed1eaf8a29801ab1163d00fb7ee4359a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/5424e678f9b304e148cf5dcc047cffc7a56a3bb5"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/81af4137a30c4c2dc694dea8cacb180bd66000ef"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/9a2d9d4e657b23dc21f24cf139e3aeff0b61341f"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a6ae4511c07b91f597e461406c6330f0d4ff810e"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c502fa9f094cb03d1d1685c71e2105ab359bc2b8"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/df4601653201de21b487c3e7fffd464790cab808"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}


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