{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-39858","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","state":"PUBLISHED","assignerShortName":"GitHub_M","dateReserved":"2026-04-07T19:13:20.379Z","datePublished":"2026-04-30T20:26:26.300Z","dateUpdated":"2026-06-30T12:09:00.290Z"},"containers":{"cna":{"title":"Traefik: Forwarded alias spoofing top pre-auth decision bypass","problemTypes":[{"descriptions":[{"cweId":"CWE-290","lang":"en","description":"CWE-290: Authentication Bypass by Spoofing","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-306","lang":"en","description":"CWE-306: Missing Authentication for Critical Function","type":"CWE"}]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"HIGH","subIntegrityImpact":"HIGH","subAvailabilityImpact":"NONE","baseScore":7.8,"baseSeverity":"HIGH","vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N","version":"4.0"}}],"references":[{"name":"https://github.com/traefik/traefik/security/advisories/GHSA-5m6w-wvh7-57vm","tags":["x_refsource_CONFIRM"],"url":"https://github.com/traefik/traefik/security/advisories/GHSA-5m6w-wvh7-57vm"},{"name":"https://github.com/traefik/traefik/releases/tag/v2.11.43","tags":["x_refsource_MISC"],"url":"https://github.com/traefik/traefik/releases/tag/v2.11.43"},{"name":"https://github.com/traefik/traefik/releases/tag/v3.6.14","tags":["x_refsource_MISC"],"url":"https://github.com/traefik/traefik/releases/tag/v3.6.14"},{"name":"https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2","tags":["x_refsource_MISC"],"url":"https://github.com/traefik/traefik/releases/tag/v3.7.0-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"}]}],"providerMetadata":{"orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","shortName":"GitHub_M","dateUpdated":"2026-04-30T20:26:26.300Z"},"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 high severity authentication bypass vulnerability in Traefik's ForwardAuth and snippet-based authentication middleware. Traefik's forwarded-header sanitization logic targets only canonical header names (e.g., X-Forwarded-Proto) and does not strip or normalize alias variants that use underscores instead of dashes (e.g., X_Forwarded_Proto). These unsanitized alias headers are forwarded intact to the authentication backend. When the backend normalizes underscore and dash header forms equivalently, an attacker can inject spoofed trust context — such as a trusted scheme or host — through the alias headers and bypass authentication on protected routes without valid credentials. This issue has been patched in versions 2.11.43, 3.6.14, and 3.7.0-rc.2."}],"source":{"advisory":"GHSA-5m6w-wvh7-57vm","discovery":"UNKNOWN"}},"adp":[{"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-05-04T16:57:57.062955Z","id":"CVE-2026-39858","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-05-04T16:58:14.458Z"}},{"affected":[{"cpes":["cpe:/a:redhat:openshift_devspaces:3.28::el9"],"defaultStatus":"affected","product":"Red Hat OpenShift Dev Spaces 3.28","vendor":"Red Hat"}],"datePublic":"2026-04-30T20:26:26.300Z","descriptions":[{"lang":"en","value":"A flaw was found in Traefik. A remote attacker can exploit an authentication bypass vulnerability by injecting spoofed trust context through unsanitized alias headers. This is due to Traefik's forwarded-header sanitization logic not properly handling alias header names that use underscores instead of dashes. This allows an attacker to bypass authentication on protected routes without valid credentials."}],"metrics":[{"other":{"content":{"namespace":"https://access.redhat.com/security/updates/classification/","value":"Important"},"type":"Red Hat severity rating"}},{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":8.2,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N","version":"3.1"},"format":"CVSS"}],"problemTypes":[{"descriptions":[{"cweId":"CWE-289","description":"Authentication Bypass by Alternate Name","lang":"en","type":"CWE"}]}],"references":[{"tags":["vdb-entry","x_refsource_REDHAT"],"url":"https://access.redhat.com/security/cve/CVE-2026-39858"},{"name":"RHBZ#2464234","tags":["issue-tracking","x_refsource_REDHAT"],"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2464234"},{"tags":["x_sadp-csaf-vex"],"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-39858.json"},{"tags":["vendor-advisory","x_refsource_REDHAT"],"url":"https://access.redhat.com/errata/RHSA-2026:21772"}],"solutions":[{"lang":"en","value":"RHSA-2026:21772: Red Hat OpenShift Dev Spaces 3.28"}],"timeline":[{"lang":"en","time":"2026-04-30T21:01:23.755Z","value":"Reported to Red Hat."},{"lang":"en","time":"2026-04-30T20:26:26.300Z","value":"Made public."}],"title":"traefik: Traefik: Authentication bypass via unsanitized alias headers","workarounds":[{"lang":"en","value":"Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability."}],"x_adpType":"supplier","x_generator":{"engine":"sadp-cli 1.0.0"},"providerMetadata":{"orgId":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c","shortName":"redhat-SADP","dateUpdated":"2026-06-30T12:09:00.290Z"}}]}}