CVE-2026-41263

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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."}, {"lang": "es", "value": "Traefik es un proxy inverso HTTP y balanceador de carga. Antes de las versiones 2.11.43, 3.6.14 y 3.7.0-rc.2, existe una vulnerabilidad de canal lateral de temporizaci\u00f3n en el middleware BasicAuth de Traefik que permite a un atacante enumerar nombres de usuario v\u00e1lidos a trav\u00e9s de diferencias en el tiempo de respuesta. La variable destinada a contener un secreto de respaldo de tiempo constante siempre se resuelve en una cadena vac\u00eda, lo que provoca que la comparaci\u00f3n de tiempo constante se interrumpa en microsegundos en lugar de realizar una evaluaci\u00f3n completa de bcrypt. Esto restaura el or\u00e1culo de temporizaci\u00f3n original y hace posible distinguir a los usuarios existentes de los no existentes midiendo los tiempos de respuesta de autenticaci\u00f3n. Este problema ha sido parcheado en las versiones 2.11.43, 3.6.14 y 3.7.0-rc.2."}], "id": "CVE-2026-41263", "lastModified": "2026-11-11T21:10:00.200", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 3.7, "baseSeverity": "LOW", "confidentialityImpact": "LOW", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N", "version": "3.1"}, "exploitabilityScore": 2.2, "impactScore": 1.4, "source": "nvd@nist.gov", "type": "Primary"}], "cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "HIGH", "attackRequirements": "NONE", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 6.3, "baseSeverity": "MEDIUM", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "LOW", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "security-advisories@github.com", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-41263", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-05-01T14:22:30.689474Z", "version": "2.0.3"}}]}, "published": "2026-04-30T21:16:33.390", "references": [{"source": "security-advisories@github.com", "tags": ["Product", "Release Notes"], "url": "https://github.com/traefik/traefik/releases/tag/v2.11.43"}, {"source": "security-advisories@github.com", "tags": ["Product", "Release Notes"], "url": "https://github.com/traefik/traefik/releases/tag/v3.6.14"}, {"source": "security-advisories@github.com", "tags": ["Product", "Release Notes"], "url": "https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2"}, {"source": "security-advisories@github.com", "tags": ["Patch", "Vendor Advisory"], "url": "https://github.com/traefik/traefik/security/advisories/GHSA-6x2q-h3cr-8j2h"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-208"}], "source": "security-advisories@github.com", "type": "Secondary"}]}

{"bugzilla": {"description": "github.com/traefik/traefik: Traefik: Username enumeration via timing side-channel in BasicAuth middleware", "id": "2464238", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2464238"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.3", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N", "status": "draft"}, "cwe": "CWE-208", "details": ["A flaw was found in Traefik. A remote attacker can exploit a timing side-channel vulnerability in Traefik's BasicAuth middleware. This flaw allows an attacker to enumerate valid usernames by observing differences in authentication response times. The vulnerability arises because a constant-time comparison, intended to prevent such attacks, short-circuits, revealing whether a username exists."], "mitigation": {"lang": "en:us", "value": "To mitigate this issue, restrict network access to Traefik instances that utilize the BasicAuth middleware. Implement firewall rules or network access controls to limit connections to trusted networks or clients only. This reduces the exposure to remote attackers attempting username enumeration. Always ensure that any changes to network configurations are thoroughly tested to prevent service disruption. A service reload or restart may be required for changes to take effect."}, "name": "CVE-2026-41263", "package_state": [{"cpe": "cpe:/a:redhat:openshift_devspaces:3", "fix_state": "Fix deferred", "package_name": "devspaces/traefik-rhel9", "product_name": "Red Hat OpenShift Dev Spaces"}], "public_date": "2026-04-30T20:39:49Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-41263\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-41263\nhttps://github.com/traefik/traefik/releases/tag/v2.11.43\nhttps://github.com/traefik/traefik/releases/tag/v3.6.14\nhttps://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2\nhttps://github.com/traefik/traefik/security/advisories/GHSA-6x2q-h3cr-8j2h"], "threat_severity": "Moderate"}

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