{"id":"CVE-2026-32665","state":"PUBLISHED","title":"Remote DNS-over-QUIC denial of service due to `quic-size` budget bypass","description":"In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, when downstream DNS-over-QUIC (DoQ) is enabled, the first two bidirectional streams on a new QUIC connection (stream_id 0 and 4) bypass the per-stream 'quic-size' gate entirely, and large input buffers are allocated later, after only the 2-byte length prefix has been received from the initial streams. As a result, a remote client can make Unbound exceed the configured 'quic-size' limit with low-cost input. Using only one connection and two streams, each sending a declared 65535-byte length prefix and then holding the streams open, a client can already trivially make Unbound roughly allocate double that amount. This is a remote availability issue / memory-accounting bypass in the downstream DoQ implementation that leads to denial of service for new DoQ clients. This vulnerability needs Unbound to be compiled with DoQ support ('--with-libngtcp2') and the 'quic-port' to be configured for the listening interfaces.","publishedAt":"2026-07-22T13:04:18.594Z","updatedAt":"2026-09-16T14:24:37.708Z","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":"1.22.0","status":"affected","lessThan":"1.25.2","versionType":"semver"}]}],"references":["https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-32665.txt"],"weaknesses":["CWE-1284"],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/32xxx/CVE-2026-32665.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-32665","state":"PUBLISHED","datePublished":"2026-07-22T13:04:18.594Z","dateUpdated":"2026-09-16T14:24:37.708Z","assignerShortName":"NLnet Labs","assignerOrgId":"206fc3a0-e175-490b-9eaa-a5738056c9f6","dateReserved":"2026-05-07T10:07:51.860Z"},"containers":{"cna":{"title":"Remote DNS-over-QUIC denial of service due to `quic-size` budget bypass","descriptions":[{"lang":"en","value":"In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, when downstream DNS-over-QUIC (DoQ) is enabled, the first two bidirectional streams on a new QUIC connection (stream_id 0 and 4) bypass the per-stream 'quic-size' gate entirely, and large input buffers are allocated later, after only the 2-byte length prefix has been received from the initial streams. As a result, a remote client can make Unbound exceed the configured 'quic-size' limit with low-cost input. Using only one connection and two streams, each sending a declared 65535-byte length prefix and then holding the streams open, a client can already trivially make Unbound roughly allocate double that amount. This is a remote availability issue / memory-accounting bypass in the downstream DoQ implementation that leads to denial of service for new DoQ clients. This vulnerability needs Unbound to be compiled with DoQ support ('--with-libngtcp2') and the 'quic-port' to be configured for the listening interfaces."}],"affected":[{"vendor":"NLnet Labs","product":"Unbound","defaultStatus":"unaffected","versions":[{"version":"1.22.0","status":"affected","lessThan":"1.25.2","versionType":"semver"}]}],"references":[{"url":"https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-32665.txt","tags":["vendor-advisory"]}],"metrics":[{"cvssV3_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","version":"3.1"},"format":"CVSS","scenarios":[{"lang":"en","value":"Unbound compiled with DoQ support ('--with-libngtcp2')"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-1284","description":"CWE-1284: Improper Validation of Specified Quantity in Input","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"NLnet Labs","orgId":"206fc3a0-e175-490b-9eaa-a5738056c9f6","dateUpdated":"2026-09-16T14:24:37.708Z"},"credits":[{"lang":"en","type":"finder","value":"N0zoM1z0 (GitHub user)"},{"lang":"en","type":"finder","value":"Kunta Chu (Tsinghua University)"},{"lang":"en","type":"finder","value":"Kaihua Wang (Tsinghua University)"},{"lang":"en","type":"finder","value":"Jianjun Chen (Tsinghua University)"},{"lang":"en","type":"finder","value":"Qifan Zhang (Palo Alto Networks)"},{"lang":"en","value":"Xuanchao Xie (University of Science and Technology of China)","type":"finder"},{"lang":"en","value":"Lutong Chen (University of Science and Technology of China)","type":"finder"},{"lang":"en","value":"Kaiping Xue (University of Science and Technology of China)","type":"finder"}],"datePublic":"2026-07-22T00:00:00.000Z","solutions":[{"lang":"en","value":"This issue is fixed starting with version 1.25.2"}],"timeline":[{"lang":"en","time":"2026-04-01T00:00:00.000Z","value":"Issue reported by N0zoM1z0"},{"lang":"en","time":"2026-04-03T00:00:00.000Z","value":"NLnet Labs shares patch with N0zoM1z0"},{"lang":"en","time":"2026-04-03T00:00:00.000Z","value":"N0zoM1z0 verifies patch"},{"lang":"en","time":"2026-04-03T00:00:00.000Z","value":"Issue reported by Kunta Chu"},{"lang":"en","time":"2026-04-09T00:00:00.000Z","value":"NLnet Labs shares patch with Kunta Chu"},{"lang":"en","time":"2026-04-03T00:00:00.000Z","value":"Kunta Chu verifies patch"},{"lang":"en","time":"2026-05-30T00:00:00.000Z","value":"Issue reported by Qifan Zhang"},{"lang":"en","time":"2026-06-15T00:00:00.000Z","value":"NLnet Labs shares patch with Qifan Zhang"},{"lang":"en","time":"2026-06-17T00:00:00.000Z","value":"Qifan Zhang verifies patch"},{"lang":"en","time":"2026-07-10T00:00:00.000Z","value":"Issue reported by Xuanchao Xie"},{"lang":"en","time":"2026-07-10T00:00:00.000Z","value":"NLnet Labs shares patch with Xuanchao Xie"},{"lang":"en","time":"2026-07-11T00:00:00.000Z","value":"Xuanchao Xie verifies patch"},{"lang":"en","time":"2026-07-22T00:00:00.000Z","value":"Fixes released with version 1.25.2"}],"x_generator":{"engine":"cvelib 1.8.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-07-22T14:31:54.691586Z","id":"CVE-2026-32665","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":"2026-07-22T14:32:02.752Z"}}]}}}