← Back to CVE Explorer

CVE-2026-46086

Full vulnerability record from the local CVENow database.

Description

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
MEDIUM
CVSS score
5.5 (v3.1)
Vulnerability status
Undergoing Analysis
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2026-05-27 14:17:30.080000
Last modified
2026-11-06 17:17:36.300000
View original CVE JSON 
{
  "id": "CVE-2026-46086",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-05-27T14:17:30.080",
  "lastModified": "2026-11-06T17:17:36.300",
  "vulnStatus": "Undergoing Analysis",
  "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->dst` to another port or to `NULL` while keeping the entry\nalive. Several bridge RCU readers inspect `f->dst`, including\n`br_fdb_fillbuf()` through the `brforward_read()` sysfs path.\n\nThese readers currently load `f->dst` 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->dst` 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->dst` in each\naffected RCU reader and using that snapshot for the rest of the access\nsequence. Also publish the in-place `f->dst` updates in `fdb_delete_local()`\nwith `WRITE_ONCE()` so the readers and writer use matching access patterns."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "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",
          "versions": [
            {
              "version": "960b589f86c74ce582922fcb996103271081f4de",
              "lessThan": "c502fa9f094cb03d1d1685c71e2105ab359bc2b8",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "960b589f86c74ce582922fcb996103271081f4de",
              "lessThan": "a6ae4511c07b91f597e461406c6330f0d4ff810e",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "960b589f86c74ce582922fcb996103271081f4de",
              "lessThan": "1406c4e0ed1eaf8a29801ab1163d00fb7ee4359a",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "960b589f86c74ce582922fcb996103271081f4de",
              "lessThan": "0b9e4bbfb7c949151e3acd44ed4aa33614d2e110",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "960b589f86c74ce582922fcb996103271081f4de",
              "lessThan": "81af4137a30c4c2dc694dea8cacb180bd66000ef",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "960b589f86c74ce582922fcb996103271081f4de",
              "lessThan": "5424e678f9b304e148cf5dcc047cffc7a56a3bb5",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "960b589f86c74ce582922fcb996103271081f4de",
              "lessThan": "9a2d9d4e657b23dc21f24cf139e3aeff0b61341f",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "960b589f86c74ce582922fcb996103271081f4de",
              "lessThan": "df4601653201de21b487c3e7fffd464790cab808",
              "versionType": "git",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "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",
          "versions": [
            {
              "version": "3.14",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "3.14",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "5.10.259",
              "lessThanOrEqual": "5.10.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "5.15.210",
              "lessThanOrEqual": "5.15.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.1.176",
              "lessThanOrEqual": "6.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.6.140",
              "lessThanOrEqual": "6.6.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.12.86",
              "lessThanOrEqual": "6.12.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.27",
              "lessThanOrEqual": "6.18.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.0.4",
              "lessThanOrEqual": "7.0.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.1",
              "lessThanOrEqual": "*",
              "versionType": "original_commit_for_fix",
              "status": "unaffected"
            }
          ]
        }
      ]
    },
    {
      "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e",
      "affectedData": [
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.6",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.7",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.6",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.7",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.6",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.7",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.6",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.7",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 TM MFP - GNU/Linux subsystem",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "0",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.6",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.7",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "[email protected]",
        "type": "Primary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "baseScore": 5.5,
          "baseSeverity": "MEDIUM",
          "attackVector": "LOCAL",
          "attackComplexity": "LOW",
          "privilegesRequired": "LOW",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 3.6
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-11-06T16:07:53.882222Z",
          "id": "CVE-2026-46086",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Primary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-476"
        }
      ]
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "operator": "OR",
          "negate": false,
          "cpeMatch": [
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "3.14.1",
              "versionEndExcluding": "5.10.259",
              "matchCriteriaId": "381832F6-7D7D-4333-9276-B44B01372277"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "5.11",
              "versionEndExcluding": "5.15.210",
              "matchCriteriaId": "5E938CDF-D1C4-43D0-98DC-9E11B6B55801"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "5.16",
              "versionEndExcluding": "6.1.176",
              "matchCriteriaId": "C4446623-5F2B-4DD8-8666-9FAAC285A757"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "6.2",
              "versionEndExcluding": "6.6.140",
              "matchCriteriaId": "A1A92866-F406-43B5-B2D1-CFC274753E9D"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "6.7",
              "versionEndExcluding": "6.12.86",
              "matchCriteriaId": "55DA1C62-9991-451E-B8A8-E0004E00F789"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "6.13",
              "versionEndExcluding": "6.18.27",
              "matchCriteriaId": "A10AC84F-C058-47D5-85B4-E6E51A613B74"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "6.19",
              "versionEndExcluding": "7.0.4",
              "matchCriteriaId": "CDB78D6D-22C3-4154-B0D0-94AF1CE5C2E3"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:3.14:-:*:*:*:*:*:*",
              "matchCriteriaId": "851B1505-0318-49F4-8D7C-196BE04FF173"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:3.14:rc3:*:*:*:*:*:*",
              "matchCriteriaId": "1795E18E-AE30-4230-809F-E40317FB96BD"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:3.14:rc4:*:*:*:*:*:*",
              "matchCriteriaId": "0F91AF02-7C23-4888-A580-07C166BE8128"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:3.14:rc5:*:*:*:*:*:*",
              "matchCriteriaId": "61A7DB5C-EB54-4D4A-AB38-8060F13C8779"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:3.14:rc6:*:*:*:*:*:*",
              "matchCriteriaId": "4FF2C86B-7087-4EFC-A256-3AF313C25325"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:3.14:rc7:*:*:*:*:*:*",
              "matchCriteriaId": "14AC6A73-D01C-44F4-9821-BAE9600E72D5"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:3.14:rc8:*:*:*:*:*:*",
              "matchCriteriaId": "055557BE-1FE9-45F5-8A95-F8D3C9B031E4"
            }
          ]
        }
      ]
    }
  ],
  "references": [
    {
      "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",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ]
    },
    {
      "url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html",
      "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"
    },
    {
      "url": "https://cert-portal.siemens.com/productcert/html/ssa-457936.html",
      "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"
    },
    {
      "url": "https://cert-portal.siemens.com/productcert/html/ssa-784472.html",
      "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"
    }
  ]
}