FKIE_CVE-2026-46086

Vulnerability from fkie_nvd - Published: 2026-05-27 14:17 - Updated: 2026-06-24 17:08
Severity
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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/0b9e4bbfb7c949151e3acd44ed4aa33614d2e110Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/1406c4e0ed1eaf8a29801ab1163d00fb7ee4359aPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/5424e678f9b304e148cf5dcc047cffc7a56a3bb5Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/81af4137a30c4c2dc694dea8cacb180bd66000efPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9a2d9d4e657b23dc21f24cf139e3aeff0b61341fPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a6ae4511c07b91f597e461406c6330f0d4ff810ePatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c502fa9f094cb03d1d1685c71e2105ab359bc2b8Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/df4601653201de21b487c3e7fffd464790cab808Patch
Impacted products
Vendor Product Version
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel 3.14
linux linux_kernel 3.14
linux linux_kernel 3.14
linux linux_kernel 3.14
linux linux_kernel 3.14
linux linux_kernel 3.14
linux linux_kernel 3.14
To clipboard 

{
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          "product": "Linux",
          "programFiles": [
            "net/bridge/br_arp_nd_proxy.c",
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          ],
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          "vendor": "Linux",
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          ],
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          "vendor": "Linux",
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              "version": "3.14"
            },
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              "version": "0",
              "versionType": "semver"
            },
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              "status": "unaffected",
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              "status": "unaffected",
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              "version": "6.12.86",
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            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.27",
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            },
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              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.4",
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            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "configurations": [
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          "negate": false,
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      ]
    }
  ],
  "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": "2026-06-24T17:08:46.907",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 5.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ]
  },
  "published": "2026-05-27T14:17:30.080",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/0b9e4bbfb7c949151e3acd44ed4aa33614d2e110"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/1406c4e0ed1eaf8a29801ab1163d00fb7ee4359a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/5424e678f9b304e148cf5dcc047cffc7a56a3bb5"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/81af4137a30c4c2dc694dea8cacb180bd66000ef"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/9a2d9d4e657b23dc21f24cf139e3aeff0b61341f"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/a6ae4511c07b91f597e461406c6330f0d4ff810e"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/c502fa9f094cb03d1d1685c71e2105ab359bc2b8"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/df4601653201de21b487c3e7fffd464790cab808"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Undergoing Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-476"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}



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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.
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  • 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.


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