{"id":"CVE-2026-123604","aliases":["GHSA-6w6g-hm98-mhgm","RUSTSEC-2026-0513"],"title":"hickory-resolver: Unbounded TC-retry loop in `NameServerPool::try_send` (resource-exhaustion DoS)","titleSource":"OSV","descriptionSource":"OSV","declaredSeverity":"HIGH","description":"When the `hickory-resolver` name server pool implementation receives an upstream response with the TC (truncated) header bit set, it re-queues the request to the same nameserver to retry with UDP transport disabled. However, the retry arm never inspects the transport that just answered and carries no iteration counter. An authoritative server that sets `TC=1` on **every** available transport  keeps the resolver spinning on one persistent TCP connection until the 5s per-request wall-clock deadline expires.\n\n### Reporter\n\nQifan Zhang, Palo Alto Networks","severity":"high","score":8.7,"published":"2026-09-03T12:00:00.000Z","modified":"2026-11-12T14:41:01.256Z","withdrawn":false,"knownExploited":false,"affected":[{"ecosystem":"crates.io","name":"hickory-resolver","sources":[{"name":"OSV · GHSA-6w6g-hm98-mhgm","url":"https://osv.dev/vulnerability/GHSA-6w6g-hm98-mhgm"}],"ranges":[{"events":[{"introduced":"0.26.0-beta.1"},{"fixed":"0.26.2"}],"type":"SEMVER"}],"versions":[],"fixed":["0.26.2"]},{"ecosystem":"crates.io","name":"hickory-resolver","sources":[{"name":"OSV · RUSTSEC-2026-0513","url":"https://osv.dev/vulnerability/RUSTSEC-2026-0513"}],"ranges":[{"events":[{"introduced":"0.26.0-beta.1"},{"fixed":"0.26.2"}],"type":"SEMVER"}],"versions":[],"fixed":["0.26.2"]}],"sourceAffected":[],"references":["https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-6w6g-hm98-mhgm","https://github.com/hickory-dns/hickory-dns/pull/3871","https://github.com/hickory-dns/hickory-dns/commit/0848d2e9e4183499343318a690d6dd5e48bc21c1","https://github.com/hickory-dns/hickory-dns/commit/5d37e2e04a36a87013a213b58b820345ef76a263","https://github.com/hickory-dns/hickory-dns","https://github.com/hickory-dns/hickory-dns/releases/tag/v0.26.2","https://crates.io/crates/hickory-resolver","https://rustsec.org/advisories/RUSTSEC-2026-0513.html","https://github.com/hickory-dns/hickory-dns/commit/f9a7bc5d188e5b680b09aea91009d2fbf3fec58a","https://www.vulncheck.com/advisories/hickory-dns-0.26.0-beta.1-before-0.26.2-resource-exhaustion-dos-via-nameserverpool-try-send-tc-retry-loop"],"sources":[{"name":"OSV","id":"GHSA-6w6g-hm98-mhgm","modified":"2026-11-12T14:41:01.256333284Z","url":"https://osv.dev/vulnerability/GHSA-6w6g-hm98-mhgm"},{"name":"OSV","id":"RUSTSEC-2026-0513","modified":"2026-11-12T14:30:06.796669440Z","url":"https://osv.dev/vulnerability/RUSTSEC-2026-0513"},{"name":"CVE","id":"CVE-2026-123604","modified":"2026-11-12T13:34:44.888Z","url":"https://www.cve.org/CVERecord?id=CVE-2026-123604"}],"assessments":[{"source":"OSV","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","score":8.7},{"source":"VulnCheck","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","score":8.7},{"source":"VulnCheck","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5}],"cve":{"records":[{"id":"CVE-2026-123604","source":"VulnCheck","state":"PUBLISHED","reasons":[],"replacements":[],"disputed":false,"unsupportedWhenAssigned":false,"reserved":"2026-11-06T01:00:16.506Z","published":"2026-11-08T01:38:31.351Z","modified":"2026-11-12T13:34:44.888Z"}],"publishers":[{"name":"VulnCheck","role":"CNA","organizationId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","modified":"2026-11-08T01:38:31.351Z"},{"name":"CISA-ADP","role":"ADP","organizationId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","modified":"2026-11-12T13:34:44.888Z"}],"references":[{"url":"https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-6w6g-hm98-mhgm","tags":["vendor-advisory"],"source":"VulnCheck"},{"url":"https://www.vulncheck.com/advisories/hickory-dns-0.26.0-beta.1-before-0.26.2-resource-exhaustion-dos-via-nameserverpool-try-send-tc-retry-loop","tags":["third-party-advisory"],"source":"VulnCheck"}],"weaknesses":[{"id":"CWE-835","description":"Loop with Unreachable Exit Condition ('Infinite Loop')","source":"VulnCheck"}],"applicability":[],"prioritization":[{"source":"CISA-ADP","type":"SSVC","role":"CISA Coordinator","timestamp":"2026-11-12T13:34:10.429278Z","decisions":[{"name":"Exploitation","value":"none"},{"name":"Automatable","value":"yes"},{"name":"Technical Impact","value":"partial"}]}]},"products":[{"vendor":"hickory-dns","name":"hickory-dns","platforms":[],"versions":[{"version":"0.26.0-beta.1","status":"affected","lessThan":"0.26.2","versionType":"semver"},{"version":"0.26.2","status":"unaffected","versionType":"semver"}],"defaultStatus":"unaffected","packageURL":"pkg:cargo/hickory-resolver","packageIdentity":{"ecosystem":"crates.io","name":"hickory-resolver"},"cpes":[],"source":"VulnCheck","url":"https://www.cve.org/CVERecord?id=CVE-2026-123604"}],"remediation":[],"observedAt":"2026-11-13T01:26:13.468Z","kev":{"status":"not-listed","checkedAt":"2026-11-15T01:55:30.737Z"},"coverage":[{"source":"NVD","status":"no-result","checkedAt":"2026-11-08T02:05:37.929Z","attemptedAt":"2026-11-08T02:05:37.929Z"},{"source":"GHSA","status":"no-result","checkedAt":"2026-11-08T02:05:37.985Z","attemptedAt":"2026-11-08T02:05:37.985Z"},{"source":"EUVD","status":"refresh-failed","attemptedAt":"2026-11-08T02:05:37.056Z"},{"source":"EPSS","status":"no-result","checkedAt":"2026-11-08T02:05:37.616Z","attemptedAt":"2026-11-08T02:05:37.616Z"}],"evidence":[],"aiSummary":{"text":"The hickory-resolver name server pool implementation has an unbounded TC-retry loop vulnerability in versions before 0.26.2, allowing an authoritative server to cause a resource-exhaustion denial-of-service by setting the TC header bit. An attacker with access to the name server pool can exploit this weakness. The impact is a potential denial-of-service.","model":"@cf/meta/llama-3.3-70b-instruct-fp8-fast","generatedAt":"2026-11-13T04:01:05.723Z","sources":[{"name":"OSV","url":"https://osv.dev/vulnerability/GHSA-6w6g-hm98-mhgm"},{"name":"OSV","url":"https://osv.dev/vulnerability/RUSTSEC-2026-0513"},{"name":"CVE","url":"https://www.cve.org/CVERecord?id=CVE-2026-123604"}]}}