{"id":"CVE-2026-82720","state":"PUBLISHED","title":"Use-after-free in DoH stream cleanup code path","description":"NLnet Labs Unbound 1.12.0 up to and including 1.26.0 has a use-after-free vulnerability when compiled for DNS-over-HTTPs support with '--with-libnghttp2'. During failure code paths (i.e., RPZ drop query, jostle due to heavy traffic), a dropped DoH stream brings down the whole DoH session and does not account properly for other DoH streams in the same session. This leads to use-after-free in those code paths. If the prerequisites are satisfied (possible RPZ drop or heavy client traffic), a malicious actor can trigger the vulnerability with a single DoH connection and the appropriate traffic. Impact is limited as the reads are not user controlled and the use-after-free leads to early returns. However, a hardened allocator can catch the use-after-free and controllably terminate the process resulting to denial of service.","publishedAt":"2026-09-16T08:32:10.359Z","updatedAt":"2026-09-16T14:14:25.720Z","severity":{"score":5.9,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/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":"1.12.0","status":"affected","lessThan":"1.26.1","versionType":"semver"}]}],"references":["https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-82720.txt"],"weaknesses":["CWE-416"],"ingestedAt":"2026-10-29T20:13:15.269Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/82xxx/CVE-2026-82720.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-82720","state":"PUBLISHED","datePublished":"2026-09-16T08:32:10.359Z","dateUpdated":"2026-09-16T14:14:25.720Z","assignerShortName":"NLnet Labs","assignerOrgId":"206fc3a0-e175-490b-9eaa-a5738056c9f6","dateReserved":"2026-09-07T14:06:21.960Z"},"containers":{"cna":{"title":"Use-after-free in DoH stream cleanup code path","descriptions":[{"lang":"en","value":"NLnet Labs Unbound 1.12.0 up to and including 1.26.0 has a use-after-free vulnerability when compiled for DNS-over-HTTPs support with '--with-libnghttp2'. During failure code paths (i.e., RPZ drop query, jostle due to heavy traffic), a dropped DoH stream brings down the whole DoH session and does not account properly for other DoH streams in the same session. This leads to use-after-free in those code paths. If the prerequisites are satisfied (possible RPZ drop or heavy client traffic), a malicious actor can trigger the vulnerability with a single DoH connection and the appropriate traffic. Impact is limited as the reads are not user controlled and the use-after-free leads to early returns. However, a hardened allocator can catch the use-after-free and controllably terminate the process resulting to denial of service."}],"affected":[{"vendor":"NLnet Labs","product":"Unbound","defaultStatus":"unaffected","versions":[{"version":"1.12.0","status":"affected","lessThan":"1.26.1","versionType":"semver"}]}],"references":[{"url":"https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-82720.txt","tags":["vendor-advisory"]}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"Compiled with DNS-over-HTTPs support"}],"cvssV3_1":{"version":"3.1","baseScore":5.9,"baseSeverity":"MEDIUM","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-416","lang":"en","description":"CWE-416: Use After Free","type":"CWE"}]}],"providerMetadata":{"shortName":"NLnet Labs","orgId":"206fc3a0-e175-490b-9eaa-a5738056c9f6","dateUpdated":"2026-09-16T08:32:10.359Z"},"datePublic":"2026-09-16T00:00:00.000Z","solutions":[{"lang":"en","value":"This issue is fixed starting with version 1.26.1"}],"timeline":[{"time":"2026-08-11T00:00:00.000Z","lang":"en","value":"Issue reported by Yuqi Qiu"},{"time":"2026-08-13T00:00:00.000Z","lang":"en","value":"NLnet Labs shares patch"},{"time":"2026-08-14T00:00:00.000Z","lang":"en","value":"Yuqi Qiu verifies patch"},{"time":"2026-09-16T00:00:00.000Z","lang":"en","value":"Fixes released with version 1.26.1"}],"credits":[{"lang":"en","value":"Yuqi Qiu (Nankai University, AOSP Lab)","type":"finder"},{"lang":"en","value":"Xiang Li (Nankai University, AOSP Lab)","type":"finder"}],"x_generator":{"engine":"cvelib 1.8.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-16T14:13:03.616721Z","id":"CVE-2026-82720","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-16T14:14:25.720Z"}}]}}}