{"id":"CVE-2026-81634","state":"PUBLISHED","title":"Possible heap buffer overflow during DNSSEC canonicalization","description":"In NLnet Labs Unbound up to and including 1.26.0, a 255 length query name with a large TCP response can lead to a heap buffer overflow during the RRSet canonicalisation routine. This is caused by missing to add the first owner name into the buffer length check. A malicious actor operating a malicious name server or tampering with an incoming response to Unbound (canonicalisation happens before DNSSEC validation), can trigger the vulnerability.","publishedAt":"2026-09-16T08:30:15.428Z","updatedAt":"2026-09-16T14:32:38.842Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","source":"NLnet Labs"},"assigner":"NLnet Labs","products":["NLnet Labs Unbound"],"affected":[{"vendor":"NLnet Labs","product":"Unbound","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"1.26.1","versionType":"semver"}]}],"references":["https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-81634.txt"],"weaknesses":["CWE-122"],"ingestedAt":"2026-10-29T20:13:15.269Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/81xxx/CVE-2026-81634.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-81634","state":"PUBLISHED","datePublished":"2026-09-16T08:30:15.428Z","dateUpdated":"2026-09-16T14:32:38.842Z","assignerShortName":"NLnet Labs","assignerOrgId":"206fc3a0-e175-490b-9eaa-a5738056c9f6","dateReserved":"2026-09-07T14:06:21.967Z"},"containers":{"cna":{"title":"Possible heap buffer overflow during DNSSEC canonicalization","descriptions":[{"lang":"en","value":"In NLnet Labs Unbound up to and including 1.26.0, a 255 length query name with a large TCP response can lead to a heap buffer overflow during the RRSet canonicalisation routine. This is caused by missing to add the first owner name into the buffer length check. A malicious actor operating a malicious name server or tampering with an incoming response to Unbound (canonicalisation happens before DNSSEC validation), can trigger the vulnerability."}],"affected":[{"vendor":"NLnet Labs","product":"Unbound","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"1.26.1","versionType":"semver"}]}],"references":[{"url":"https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-81634.txt","tags":["vendor-advisory"]}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV3_1":{"version":"3.1","baseScore":7.5,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-122","lang":"en","description":"CWE-122: Heap-based Buffer Overflow","type":"CWE"}]}],"providerMetadata":{"shortName":"NLnet Labs","orgId":"206fc3a0-e175-490b-9eaa-a5738056c9f6","dateUpdated":"2026-09-16T08:30:15.428Z"},"datePublic":"2026-09-16T00:00:00.000Z","solutions":[{"lang":"en","value":"This issue is fixed starting with version 1.26.1"}],"timeline":[{"time":"2026-07-31T00:00:00.000Z","lang":"en","value":"Issue reported by Vlatko Kosturjak"},{"time":"2026-08-03T00:00:00.000Z","lang":"en","value":"NLnet Labs shares patch"},{"time":"2026-08-04T00:00:00.000Z","lang":"en","value":"Vlatko Kosturjak verifies patch"},{"time":"2026-09-16T00:00:00.000Z","lang":"en","value":"Fixes released with version 1.26.1"}],"credits":[{"lang":"en","value":"Vlatko Kosturjak (Marlink Cyber)","type":"finder"}],"x_generator":{"engine":"cvelib 1.8.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-16T14:32:31.803030Z","id":"CVE-2026-81634","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-16T14:32:38.842Z"}}]}}}