{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-88879 in the wild and no public exploit code.","fix":"Change a configuration setting.","what":"CVE-2026-88879 is a medium-severity authentication bypass vulnerability in Traefik Traefik, published on 10 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-88879 and fix it if it is affected.\n\nWhat it is: CVE-2026-88879 is a medium-severity authentication bypass vulnerability in Traefik Traefik, published on 10 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-88879 in the wild and no public exploit code.\n\nAffected product: Traefik Traefik. No package-level version data is available, so check the vendor advisory linked from the reference page.\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-88879/ (Markdown: https://insights.sbomify.com/CVE-2026-88879/index.md)","id":"CVE-2026-88879","markdown":"https://insights.sbomify.com/CVE-2026-88879/index.md","name":"CVE-2026-88879","record":{"aliases":["GHSA-cwr6-3wm2-9xhw","MINI-m3mx-vhvw-52ww","MINI-r6ff-6p33-32xr","MINI-v23m-c3ph-2j7p"],"analysis":{"component_type":"server_software","fix_type":"configuration_change","impacts":["privilege_escalation","security_bypass"],"network_reachable":"yes","non_default_config":true,"product_category":"Traefik reverse proxy","requires_auth":"low_privilege","summary":"Attackers can spoof identity headers to bypass authentication and escalate privileges in backends by exploiting header canonicalization flaws in Traefik.","user_interaction":"not_required","vuln_class":"auth_bypass"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"VulnCheck","cpe":[{"product":"traefik","vendor":"traefik"}],"cvss":{"score":5.3,"severity":"medium","source":"cna","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N","version":"4.0"},"cwes":[{"id":"CWE-290","name":"Authentication Bypass by Spoofing"}],"description":"Traefik is an HTTP reverse proxy and load balancer. In Traefik v1.x, v2.x through v2.11.55, and v3.0.0 through v3.7.11, header names are canonicalized only on dashes, so X-Auth-User, X_Auth_User and X.Auth.User are treated as three distinct headers by Traefik, while backends that derive variable names from header names (CGI, WSGI, PHP, NGINX and others) collapse them into a single variable. A client can therefore smuggle a dot-form alias of a header that Traefik manages past the middleware managing it — for example supplying X.Authenticated.User alongside the canonical X-Authenticated-User written by the ForwardAuth middleware — causing such a backend to read the client-supplied value instead of the identity Traefik asserted. In the tested configuration (PHP 8.2 built-in SAPI over an HTTP/1 backend path), Go's lexical header ordering makes the attacker-supplied value win deterministically, so a client that ForwardAuth admits as a low-privilege identity can be treated by the backend as a different user or role. Any header Traefik sets is affected, not only ForwardAuth's. This is an incomplete fix for GHSA-x677-9fxg-v5c5, which blocked only the underscore form. Fixed in v2.11.56 and v3.7.12, which add the aliasHeadersStrategy entry-point option; because it defaults to 'keep' for backwards compatibility, it must be explicitly set to 'delete' or 'reject' for the fix to take effect. Unmaintained release lines will not receive a patch.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"Traefik before v2.11.56 Identity Spoofing via Header Alias","id":"CVE-2026-88879","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":"traefik:traefik","products":["traefik:traefik"],"type":"auth_bypass","year":"2026"},"n_packages":0,"n_references":2,"next":{"headline":"Renovate before 44.11.3 Credential Exfiltration via Link Header","id":"CVE-2026-88880"},"packages":[],"prev":{"headline":"Traefik v2.8.2 through v3.6 HTTP/3 Timeout Bypass","id":"CVE-2026-88878"},"products":["traefik"],"published":"2026-09-10","related":[{"cvss_score":9.8,"headline":"HTTP client can remove the X-Forwarded headers in Traefik","id":"CVE-2024-45410","kev_date_added":null,"published":"2024-09-19"},{"cvss_score":9.3,"headline":"Traefik v3.7.0 Authentication Bypass via from-to-www-redirect","id":"CVE-2026-88877","kev_date_added":null,"published":"2026-09-10"},{"cvss_score":9.3,"headline":"Traefik before v2.11.55 and v3.0.0 through v3.7.10 Authentication Bypass via digestAuth","id":"CVE-2026-85595","kev_date_added":null,"published":"2026-09-04"},{"cvss_score":9.1,"headline":"Traefik HTTP/3 Backend NTLM Connection Reuse","id":"CVE-2026-88007","kev_date_added":null,"published":"2026-09-10"},{"cvss_score":8.8,"headline":"Traefik: Rootless HTTP/1 request-target routes as \"/\" but is forwarded verbatim, bypassing path-scoped routing, middleware guards and access logging","id":"CVE-2026-88009","kev_date_added":null,"published":"2026-09-10"},{"cvss_score":8.8,"headline":"Traefik has a possible vulnerability with the path matchers","id":"CVE-2025-32431","kev_date_added":null,"published":"2025-04-21"},{"cvss_score":8.2,"headline":"Traefik v3.7 Authentication Bypass via TLS Option Conflict","id":"CVE-2026-85596","kev_date_added":null,"published":"2026-09-04"}],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"US public information, NVD API terms","name":"NVD"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"no","exploitation":"none","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-10-08","vendors":["traefik"]},"summary":"Attackers can spoof identity headers to bypass authentication and escalate privileges in backends by exploiting header canonicalization flaws in Traefik.","url":"https://insights.sbomify.com/CVE-2026-88879/"}