CVE-2026-53921 (GCVE-0-2026-53921)

Vulnerability from cvelistv5 – Published: 2026-10-23 13:20 – Updated: 2026-10-23 13:20
VLAI
Title
odhcpd: Stack buffer overflow in DHCPv6 IA reply serialization (2 independent sites)
Summary
odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt. Prior to version 25.12, odhcpd's DHCPv6 IA response handler writes past the end of a fixed 512-byte stack buffer (pdbuf) when a single DHCPv6 REQUEST carries enough IA options to nearly exhaust the reply space. Two independent overflow sites exist in the same call chain, both reachable from the network via a single unauthenticated UDP packet. odhcpd runs as root on OpenWrt; embedded targets often lack stack canaries and ASLR, making code execution realistic. This issue has been patched in version 25.12.
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE
  • CWE-121 - Stack-based Buffer Overflow
Assigner
GitHub_M CNA under the mitre root
CNA scorecard C 72/100 over 7760 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
openwrt odhcpd Affected: < 25.12
guessed Create a notification for this product.
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "odhcpd",
          "vendor": "openwrt",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 25.12"
            }
          ]
        }
      ],
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        {
          "lang": "en",
          "value": "odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt. Prior to version 25.12, odhcpd\u0027s DHCPv6 IA response handler writes past the end of a fixed 512-byte stack buffer (pdbuf) when a single DHCPv6 REQUEST carries enough IA options to nearly exhaust the reply space. Two independent overflow sites exist in the same call chain, both reachable from the network via a single unauthenticated UDP packet. odhcpd runs as root on OpenWrt; embedded targets often lack stack canaries and ASLR, making code execution realistic. This issue has been patched in version 25.12."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
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          "descriptions": [
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              "cweId": "CWE-121",
              "description": "CWE-121: Stack-based Buffer Overflow",
              "lang": "en",
              "type": "CWE"
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      "providerMetadata": {
        "dateUpdated": "2026-10-23T13:20:30.249Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
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          "name": "https://github.com/openwrt/odhcpd/security/advisories/GHSA-7fwx-hhrg-3496",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/openwrt/odhcpd/security/advisories/GHSA-7fwx-hhrg-3496"
        },
        {
          "name": "https://github.com/openwrt/odhcpd/commit/0320032ae313452f3c8cb8725c621dd06c36dc03",
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          "tags": [
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          ],
          "url": "https://github.com/openwrt/odhcpd/commit/03dacc23356b5789842b9d1bba0200fd005e35f3"
        },
        {
          "name": "https://github.com/openwrt/odhcpd/commit/2a42d34c3615e2449ca273f673eee7c429d819a9",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/openwrt/odhcpd/commit/2a42d34c3615e2449ca273f673eee7c429d819a9"
        },
        {
          "name": "https://github.com/openwrt/odhcpd/commit/6634b7a3c79c41a27687925c98c35c8aea2f2b5a",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/openwrt/odhcpd/commit/6634b7a3c79c41a27687925c98c35c8aea2f2b5a"
        },
        {
          "name": "https://github.com/openwrt/odhcpd/commit/d168c27fb6a55a07ac4c888e09ff2f41e263d7b7",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/openwrt/odhcpd/commit/d168c27fb6a55a07ac4c888e09ff2f41e263d7b7"
        },
        {
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          "tags": [
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          ],
          "url": "https://github.com/openwrt/odhcpd/commit/d329a15413387027453644cd363dca06ade28328"
        }
      ],
      "source": {
        "advisory": "GHSA-7fwx-hhrg-3496",
        "discovery": "UNKNOWN"
      },
      "title": "odhcpd: Stack buffer overflow in DHCPv6 IA reply serialization (2 independent sites)"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-53921",
    "datePublished": "2026-10-23T13:20:30.249Z",
    "dateReserved": "2026-06-11T15:46:12.316Z",
    "dateUpdated": "2026-10-23T13:20:30.249Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-53921",
      "date": "2026-10-25",
      "epss": "0.01123",
      "percentile": "0.66"
    },
    "nvd": {
      "cve": {
        "affected": [
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                "product": "odhcpd",
                "vendor": "openwrt",
                "versions": [
                  {
                    "status": "affected",
                    "version": "\u003c 25.12"
                  }
                ]
              }
            ],
            "source": "security-advisories@github.com"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt. Prior to version 25.12, odhcpd\u0027s DHCPv6 IA response handler writes past the end of a fixed 512-byte stack buffer (pdbuf) when a single DHCPv6 REQUEST carries enough IA options to nearly exhaust the reply space. Two independent overflow sites exist in the same call chain, both reachable from the network via a single unauthenticated UDP packet. odhcpd runs as root on OpenWrt; embedded targets often lack stack canaries and ASLR, making code execution realistic. This issue has been patched in version 25.12."
          }
        ],
        "id": "CVE-2026-53921",
        "lastModified": "2026-10-23T19:37:11.060",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 9.8,
                "baseSeverity": "CRITICAL",
                "confidentialityImpact": "HIGH",
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                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
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        "references": [
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            "url": "https://github.com/openwrt/odhcpd/commit/0320032ae313452f3c8cb8725c621dd06c36dc03"
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          }
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        "vulnStatus": "Deferred",
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              }
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            "source": "security-advisories@github.com",
            "type": "Primary"
          }
        ]
      }
    }
  }
}



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