{"id":"CVE-2026-5950","state":"PUBLISHED","title":"Unbounded resend loop in BIND 9 resolver","description":"An unbounded resend loop vulnerability exists in the BIND 9 resolver state machine during bad-server handling, enabling a remote unauthenticated attacker to cause severe resource exhaustion by sending queries that trigger specific retry conditions.\nThis issue affects BIND 9 versions 9.18.36 through 9.18.48, 9.20.8 through 9.20.22, 9.21.7 through 9.21.21, 9.18.36-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.","publishedAt":"2026-05-20T13:10:19.989Z","updatedAt":"2026-05-20T13:38:53.211Z","severity":{"score":5.3,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","source":"isc"},"assigner":"isc","products":["ISC BIND 9"],"affected":[{"vendor":"ISC","product":"BIND 9","defaultStatus":"unaffected","versions":[{"version":"9.18.36","status":"affected","lessThanOrEqual":"9.18.48","versionType":"custom"},{"version":"9.20.8","status":"affected","lessThanOrEqual":"9.20.22","versionType":"custom"},{"version":"9.21.7","status":"affected","lessThanOrEqual":"9.21.21","versionType":"custom"},{"version":"9.18.36-S1","status":"affected","lessThanOrEqual":"9.18.48-S1","versionType":"custom"},{"version":"9.20.9-S1","status":"affected","lessThanOrEqual":"9.20.22-S1","versionType":"custom"}]}],"references":["https://kb.isc.org/docs/cve-2026-5950","https://downloads.isc.org/isc/bind9/9.18.49","https://downloads.isc.org/isc/bind9/9.20.23","https://downloads.isc.org/isc/bind9/9.21.22"],"weaknesses":["CWE-606"],"ingestedAt":"2026-10-29T20:12:32.778Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/5xxx/CVE-2026-5950.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-5950","state":"PUBLISHED","datePublished":"2026-05-20T13:10:19.989Z","dateUpdated":"2026-05-20T13:38:53.211Z","assignerShortName":"isc","assignerOrgId":"404fd4d2-a609-4245-b543-2c944a302a22","dateReserved":"2026-04-09T06:42:23.953Z"},"containers":{"cna":{"title":"Unbounded resend loop in BIND 9 resolver","descriptions":[{"lang":"en","value":"An unbounded resend loop vulnerability exists in the BIND 9 resolver state machine during bad-server handling, enabling a remote unauthenticated attacker to cause severe resource exhaustion by sending queries that trigger specific retry conditions.\nThis issue affects BIND 9 versions 9.18.36 through 9.18.48, 9.20.8 through 9.20.22, 9.21.7 through 9.21.21, 9.18.36-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1."}],"affected":[{"vendor":"ISC","product":"BIND 9","defaultStatus":"unaffected","versions":[{"version":"9.18.36","status":"affected","lessThanOrEqual":"9.18.48","versionType":"custom"},{"version":"9.20.8","status":"affected","lessThanOrEqual":"9.20.22","versionType":"custom"},{"version":"9.21.7","status":"affected","lessThanOrEqual":"9.21.21","versionType":"custom"},{"version":"9.18.36-S1","status":"affected","lessThanOrEqual":"9.18.48-S1","versionType":"custom"},{"version":"9.20.9-S1","status":"affected","lessThanOrEqual":"9.20.22-S1","versionType":"custom"}]}],"references":[{"url":"https://kb.isc.org/docs/cve-2026-5950","name":"CVE-2026-5950","tags":["vendor-advisory"]},{"url":"https://downloads.isc.org/isc/bind9/9.18.49","tags":["patch"]},{"url":"https://downloads.isc.org/isc/bind9/9.20.23","tags":["patch"]},{"url":"https://downloads.isc.org/isc/bind9/9.21.22","tags":["patch"]}],"metrics":[{"cvssV3_1":{"version":"3.1","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"LOW","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","baseScore":5.3,"baseSeverity":"MEDIUM"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-606","lang":"en","type":"CWE","description":"CWE-606 Unchecked Input for Loop Condition"}]}],"providerMetadata":{"shortName":"isc","orgId":"404fd4d2-a609-4245-b543-2c944a302a22","dateUpdated":"2026-05-20T13:10:19.989Z"},"datePublic":"2026-05-20T00:00:00.000Z","cpeApplicability":[{"nodes":[{"operator":"OR","cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*","versionStartIncluding":"9.18.36","versionEndIncluding":"9.18.48"},{"vulnerable":true,"criteria":"cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*","versionStartIncluding":"9.20.8","versionEndIncluding":"9.20.22"},{"vulnerable":true,"criteria":"cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*","versionStartIncluding":"9.21.7","versionEndIncluding":"9.21.21"},{"vulnerable":true,"criteria":"cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*","versionStartIncluding":"9.18.36-S1","versionEndIncluding":"9.18.48-S1"},{"vulnerable":true,"criteria":"cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*","versionStartIncluding":"9.20.9-S1","versionEndIncluding":"9.20.22-S1"}]}]}],"impacts":[{"descriptions":[{"lang":"en","value":"Severe resource exhaustion."}]}],"workarounds":[{"lang":"en","value":"No workarounds known."}],"exploits":[{"lang":"en","value":"We are not aware of any active exploits."}],"solutions":[{"lang":"en","value":"Upgrade to the patched release most closely related to your current version of BIND 9: 9.18.49, 9.20.23, 9.21.22, 9.18.49-S1, or 9.20.23-S1."}],"credits":[{"lang":"en","value":"ISC would like to thank Billy Baraja (BielraX) for bringing this vulnerability to our attention."}],"source":{"discovery":"EXTERNAL"},"x_generator":{"engine":"cvelib 1.8.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-05-20T13:38:40.421994Z","id":"CVE-2026-5950","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":"2026-05-20T13:38:53.211Z"}}]}}}