{"id":"CVE-2026-41263","state":"PUBLISHED","title":"Traefik: BasicAuth middleware: timing side-channel vulnerability","description":"Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a timing side-channel vulnerability in Traefik's BasicAuth middleware that allows an attacker to enumerate valid usernames through response-time differences. The variable intended to hold a constant-time fallback secret always resolves to an empty string, causing the constant-time comparison to short-circuit in microseconds rather than performing a full bcrypt evaluation. This restores the original timing oracle and makes it possible to distinguish existing users from non-existing ones by measuring authentication response times. This issue has been patched in versions 2.11.43, 3.6.14, and 3.7.0-rc.2.","publishedAt":"2026-04-30T20:39:49.658Z","updatedAt":"2026-05-01T14:22:40.566Z","severity":{"score":6.3,"label":"Medium","version":"4.0","vector":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["traefik traefik"],"affected":[{"vendor":"traefik","product":"traefik","versions":[{"version":"< 2.11.43","status":"affected"},{"version":">= 3.0.0-beta1, < 3.6.14","status":"affected"},{"version":">= 3.7.0-ea.1, < 3.7.0-rc.2","status":"affected"}]}],"references":["https://github.com/traefik/traefik/security/advisories/GHSA-6x2q-h3cr-8j2h","https://github.com/traefik/traefik/releases/tag/v2.11.43","https://github.com/traefik/traefik/releases/tag/v3.6.14","https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2"],"weaknesses":["CWE-208"],"ingestedAt":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/41xxx/CVE-2026-41263.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-41263","state":"PUBLISHED","datePublished":"2026-04-30T20:39:49.658Z","dateUpdated":"2026-05-01T14:22:40.566Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-04-18T14:01:46.801Z"},"containers":{"cna":{"title":"Traefik: BasicAuth middleware: timing side-channel vulnerability","descriptions":[{"lang":"en","value":"Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a timing side-channel vulnerability in Traefik's BasicAuth middleware that allows an attacker to enumerate valid usernames through response-time differences. The variable intended to hold a constant-time fallback secret always resolves to an empty string, causing the constant-time comparison to short-circuit in microseconds rather than performing a full bcrypt evaluation. This restores the original timing oracle and makes it possible to distinguish existing users from non-existing ones by measuring authentication response times. This issue has been patched in versions 2.11.43, 3.6.14, and 3.7.0-rc.2."}],"affected":[{"vendor":"traefik","product":"traefik","versions":[{"version":"< 2.11.43","status":"affected"},{"version":">= 3.0.0-beta1, < 3.6.14","status":"affected"},{"version":">= 3.7.0-ea.1, < 3.7.0-rc.2","status":"affected"}]}],"references":[{"url":"https://github.com/traefik/traefik/security/advisories/GHSA-6x2q-h3cr-8j2h","name":"https://github.com/traefik/traefik/security/advisories/GHSA-6x2q-h3cr-8j2h","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/traefik/traefik/releases/tag/v2.11.43","name":"https://github.com/traefik/traefik/releases/tag/v2.11.43","tags":["x_refsource_MISC"]},{"url":"https://github.com/traefik/traefik/releases/tag/v3.6.14","name":"https://github.com/traefik/traefik/releases/tag/v3.6.14","tags":["x_refsource_MISC"]},{"url":"https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2","name":"https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"HIGH","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"LOW","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":6.3,"baseSeverity":"MEDIUM","vectorString":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N","version":"4.0"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-208","lang":"en","description":"CWE-208: Observable Timing Discrepancy","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-04-30T20:39:49.658Z"},"source":{"advisory":"GHSA-6x2q-h3cr-8j2h","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-05-01T14:22:30.689474Z","id":"CVE-2026-41263","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":"2026-05-01T14:22:40.566Z"}}]}}}