CVE-2026-112112 (GCVE-0-2026-112112)

Vulnerability from cvelistv5 – Published: 2026-10-18 23:01 – Updated: 2026-10-18 23:01
VLAI
Summary
An IPv6 FlowSpec validation bypass in the CZ.NIC BIRD Internet Routing Daemon allows an established BGP peer to inject FlowSpec rules matching destinations outside the address space authorized by the unicast-route validation procedure. With validation enabled on the receiving flow6 channel, BIRD fails to reject a destination prefix component with a nonzero offset, contrary to RFC 8956 section 5. It validates a reconstructed prefix with zero-filled skipped bits, although the original FlowSpec component can match a broader set of IPv6 addresses. Given a suitable unicast route from the peer, the rule can pass validation and, where export policy permits, be propagated to downstream peers. Downstream enforcement may cause unauthorized traffic filtering or redirection.
Severity
2.3 (Low)
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
CWE
  • CWE-1284 - Improper Validation of Specified Quantity in Input
Assigner
mitre CNA under the mitre root
CNA scorecard E 28/100 over 2338 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
nic BIRD Affected: 2.0.9 , ≤ 2.20.0 (semver)
Affected: 3.0.0 , ≤ 3.4.0 (semver)
    cpe:2.3:a:nic:bird:*:*:*:*:*:*:*:*
    cpe:2.3:a:nic:bird:*:*:*:*:*:*:*:*
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unknown",
          "modules": [
            "IPv6 FlowSpec validation"
          ],
          "product": "BIRD",
          "programFiles": [
            "nest/rt-table.c"
          ],
          "programRoutines": [
            {
              "name": "net_flow_has_dst_prefix"
            }
          ],
          "repo": "https://gitlab.nic.cz/labs/bird",
          "vendor": "nic",
          "versions": [
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              "status": "affected",
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            },
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              "value": "\u003cp\u003eAn established BGP peer must be able to send IPv6 FlowSpec to a receiving flow6 channel configured with \"validate yes\". A suitable unicast route from that peer must be present in the base table. Propagation additionally requires an export policy permitting the rule. Data-plane impact depends on downstream support for, acceptance of, and enforcement of the FlowSpec match and action.\u003c/p\u003e"
            }
          ],
          "value": "An established BGP peer must be able to send IPv6 FlowSpec to a receiving flow6 channel configured with \"validate yes\". A suitable unicast route from that peer must be present in the base table. Propagation additionally requires an export policy permitting the rule. Data-plane impact depends on downstream support for, acceptance of, and enforcement of the FlowSpec match and action."
        }
      ],
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                  "versionEndIncluding": "2.20.0",
                  "versionStartIncluding": "2.0.9",
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                },
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        }
      ],
      "metrics": [
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            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 2.3,
            "baseSeverity": "LOW",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
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              "cweId": "CWE-1284",
              "description": "CWE-1284 Improper Validation of Specified Quantity in Input",
              "lang": "en",
              "type": "CWE"
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          ]
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      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-18T23:01:05.633Z",
        "orgId": "8254265b-2729-46b6-b9e3-3dfca2d5bfca",
        "shortName": "mitre"
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      "references": [
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          "url": "https://gitlab.nic.cz/labs/bird/-/commit/7cf75587b6f38b87849fe192bf5dfd124b7702bc"
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        {
          "url": "https://www.rfc-editor.org/rfc/rfc8956.html#section-5"
        },
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          "url": "https://gitlab.nic.cz/labs/bird/-/blob/v2.20.0/nest/rt-table.c#L2686"
        },
        {
          "url": "https://gitlab.nic.cz/labs/bird/-/blob/v3.4.0/nest/rt-table.c#L4518"
        }
      ],
      "solutions": [
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          "lang": "en",
          "supportingMedia": [
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              "type": "text/html",
              "value": "\u003cp\u003eApply upstream commit 7cf75587b6f38b87849fe192bf5dfd124b7702bc or a verified branch-specific backport. The fix requires the original IPv6 destination-prefix component to have offset zero before it can pass FlowSpec validation. The first fixed release has not yet been verified.\u003c/p\u003e"
            }
          ],
          "value": "Apply upstream commit 7cf75587b6f38b87849fe192bf5dfd124b7702bc or a verified branch-specific backport. The fix requires the original IPv6 destination-prefix component to have offset zero before it can pass FlowSpec validation. The first fixed release has not yet been verified."
        }
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  "cveMetadata": {
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    "assignerShortName": "mitre",
    "cveId": "CVE-2026-112112",
    "datePublished": "2026-10-18T23:01:05.633Z",
    "dateReserved": "2026-10-18T23:01:05.103Z",
    "dateUpdated": "2026-10-18T23:01:05.633Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": {
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        "affected": [
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              {
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                "modules": [
                  "IPv6 FlowSpec validation"
                ],
                "product": "BIRD",
                "programFiles": [
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                ],
                "programRoutines": [
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                    "name": "net_flow_has_dst_prefix"
                  }
                ],
                "repo": "https://gitlab.nic.cz/labs/bird",
                "vendor": "nic",
                "versions": [
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        "descriptions": [
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            "lang": "en",
            "value": "An IPv6 FlowSpec validation bypass in the CZ.NIC BIRD Internet Routing Daemon allows an established BGP peer to inject FlowSpec rules matching destinations outside the address space authorized by the unicast-route validation procedure. With validation enabled on the receiving flow6 channel, BIRD fails to reject a destination prefix component with a nonzero offset, contrary to RFC 8956 section 5. It validates a reconstructed prefix with zero-filled skipped bits, although the original FlowSpec component can match a broader set of IPv6 addresses. Given a suitable unicast route from the peer, the rule can pass validation and, where export policy permits, be propagated to downstream peers. Downstream enforcement may cause unauthorized traffic filtering or redirection."
          }
        ],
        "id": "CVE-2026-112112",
        "lastModified": "2026-10-18T23:16:56.767",
        "metrics": {
          "cvssMetricV40": [
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                "Automatable": "NOT_DEFINED",
                "Recovery": "NOT_DEFINED",
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                "availabilityRequirement": "NOT_DEFINED",
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                "confidentialityRequirement": "NOT_DEFINED",
                "exploitMaturity": "NOT_DEFINED",
                "integrityRequirement": "NOT_DEFINED",
                "modifiedAttackComplexity": "NOT_DEFINED",
                "modifiedAttackRequirements": "NOT_DEFINED",
                "modifiedAttackVector": "NOT_DEFINED",
                "modifiedPrivilegesRequired": "NOT_DEFINED",
                "modifiedSubAvailabilityImpact": "NOT_DEFINED",
                "modifiedSubConfidentialityImpact": "NOT_DEFINED",
                "modifiedSubIntegrityImpact": "NOT_DEFINED",
                "modifiedUserInteraction": "NOT_DEFINED",
                "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
                "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
                "modifiedVulnIntegrityImpact": "NOT_DEFINED",
                "privilegesRequired": "LOW",
                "providerUrgency": "NOT_DEFINED",
                "subAvailabilityImpact": "NONE",
                "subConfidentialityImpact": "NONE",
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                "userInteraction": "NONE",
                "valueDensity": "NOT_DEFINED",
                "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
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        "vulnStatus": "Received",
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}



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