Evidence used
- No CISA KEV confirmation is currently recorded.
- EPSS is 0.42% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2026
CVE-2026-88011High confidence
Traefik: ForwardAuth identity spoofing via dot-form header alias
traefik · traefik
Official source article: GitHub GHSA-RF44-J88R-HH8C ↗. Check the applicable product and release in the original source.
5.3MediumCVSS 4.0
Patch only the product branches with a verified fix
Fix availability varies by productMedium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority. Verified remediation exists for at least one product or source, but 1 structured product or package state remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityMedium→Operational priority:Medium, unchanged from published severity.unchanged
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict the affected network interface to trusted sources where business-safe.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs traefik traefik and falls inside the recorded affected range.
- Verify the installed build against the product-specific fixed version after deployment.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Remediation availability differs by product scope
Verified remediation exists for at least one product or source, but 1 structured product or package state remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
- Red Hat Product Security: 1 affected or under-investigation product state without a fixed product state in the same current advisory
Open-source package ranges2 source-attributed ranges
These OSV and GitHub advisory ranges apply only to the named package and ecosystem. A listed fixed version is not a universal product patch or proof that an update is installed.
| Ecosystem and package | Affected range | First fixed version | Evidence |
|---|---|---|---|
| gogithub.com/traefik/traefik/v2 | < 2.11.56 | 2.11.56 | GitHub advisory ↗upstream repository advisory · 10 Sep 2026 |
| gogithub.com/traefik/traefik/v3 | >= 3.0.0, < 3.7.12 | 3.7.12 | GitHub advisory ↗upstream repository advisory · 10 Sep 2026 |
Direct vendor intelligence
1 currentAuthoritative vendor CSAF and VEX advisories
Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.
CVE-2026-88011 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitygithub.com/traefik/traefik: Traefik: Identity spoofing via dot-form header alias
The vendor explicitly identifies these products as affected by this CVE.
- devspaces/traefik-rhel9 as a component of Red Hat OpenShift Dev Spaces
- Summary
- A flaw was found in Traefik, an open-source HTTP reverse proxy and load balancer. A remote attacker can exploit this vulnerability by sending a specially crafted dot-form header, such as X.Authenticated.User. Due to a discrepancy in how Go and certain backend systems (like CGI, WSGI, PHP, and NGINX) interpret these headers, the backend may consume the client's supplied value instead of the identity asserted by Traefik. This allows for identity spoofing for any header managed by Traefik, potentially leading to unauthorized access or actions.
- Remediation
- Update Traefik to 2.11.56 or 3.7.12 (or later) and explicitly configure entrypoints with 'aliasHeadersStrategy: delete' or 'aliasHeadersStrategy: reject', as the feature defaults to 'keep' for backward compatibility.
Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority. Verified remediation exists for at least one product or source, but 1 structured product or package state remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
Fix availability varies by product01
What, why and how
Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.56, and from 3.0.0 until 3.7.12, a client-supplied dot-form header such as X.Authenticated.User survives ForwardAuth replacement and underscoreHeadersStrategy because Go treats it as distinct from X-Authenticated-User while normalization-prone CGI, WSGI, PHP, and NGINX backends collapse both names. A backend can consequently consume the client value instead of the identity Traefik asserted, allowing identity spoofing for any header managed by Traefik. The aliasHeadersStrategy protection is disabled by default and must be configured as delete or reject. The mitigation is available in 2.11.56 and 3.7.12.
What
Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.56, and from 3.0.0 until 3.7.12, a client-supplied dot-form header such as X.Authenticated.User survives ForwardAuth replacement and underscoreHeadersStrategy because Go treats it as distinct from X-Authenticated-User while normalization-prone CGI, WSGI, PHP, and NGINX backends collapse both names. A backend can consequently consume the client value instead of the identity Traefik asserted, allowing identity spoofing for any header managed by Traefik. The aliasHeadersStrategy protection is disabled by default and must be configured as delete or reject. The mitigation is available in 2.11.56 and 3.7.12.
Why
This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks.
How
An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.56, and from 3.0.0 until 3.7.12, a client-supplied dot-form header such as X.Authenticated.User survives ForwardAuth replacement and underscoreHeadersStrategy because Go treats it as distinct from X-Authenticated-User while normalization-prone CGI, WSGI, PHP, and NGINX backends collapse both names. A backend can consequently consume the client value instead of the identity Traefik asserted, allowing identity spoofing for any header managed by Traefik. The aliasHeadersStrategy protection is disabled by default and must be configured as delete or reject. The mitigation is available in 2.11.56 and 3.7.12.
Why
This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks.
How
An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.
- Likely attack path
- a network path → Authentication Bypass by Spoofing → cause the confidentiality, integrity or availability impact described by the vendor
- Attack surface
- Network
- Privileges required
- Low: a basic authenticated account is required
- User interaction
- None
- Attack complexity
- Low: no specialised conditions are recorded
- Security boundary
- Not a CVSS 4.0 base metric
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-290 ↗
CWE-290: Authentication Bypass by Spoofing. This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:NCommon Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.ATPresentAttack requirements: A particular deployment or execution condition must be present.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.VCNoneVulnerable-system confidentiality: No direct loss is represented by this metric.VINoneVulnerable-system integrity: No direct loss is represented by this metric.VANoneVulnerable-system availability: No direct loss is represented by this metric.SCHighSubsequent-system confidentiality: A successful attack can cause a major loss.SIHighSubsequent-system integrity: A successful attack can cause a major loss.SANoneSubsequent-system availability: No direct loss is represented by this metric.- Post-exploitation / living off the land
- No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
03
Patch and workaround
Operational remediation based on structured source evidence.
- Status
?
Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change. - Fix availability varies by product
- Action
- Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
- Workaround
- Update Traefik to 2.11.56 or 3.7.12 (or later) and explicitly configure entrypoints with 'aliasHeadersStrategy: delete' or 'aliasHeadersStrategy: reject', as the feature defaults to 'keep' for backward compatibility.
Official vendor articles3 stored documents
Linked articles are downloaded and versioned as source evidence. A CVE mention or approved update relationship does not, by itself, verify a fix for every product branch.
- ForwardAuth identity spoofing via dot-form header alias · Advisory · traefik/traefik · GitHub →Original publisher ↗Searchable text snapshot · Captured 27 Sep 2026traefik / traefik Public Uh oh! There was an error while loading. Please reload this page . Notifications You must be signed in to change notification settings Fork 6.2k Star 65k Code Issues 686 Pull requests 246 Actions Projects Security and quality 75 Insights Additional navigation options Code Issue
- Release v2.11.56 · traefik/traefik · GitHub →Original publisher ↗Searchable text snapshot · Captured 26 Sep 2026traefik / traefik Public Uh oh! There was an error while loading. Please reload this page . Notifications You must be signed in to change notification settings Fork 6.2k Star 65k Code Issues 686 Pull requests 246 Actions Projects Security and quality 75 Insights Additional navigation options Code Issue
- Release v3.7.12 · traefik/traefik · GitHub →Original publisher ↗Searchable text snapshot · Captured 26 Sep 2026traefik / traefik Public Uh oh! There was an error while loading. Please reload this page . Notifications You must be signed in to change notification settings Fork 6.2k Star 65k Code Issues 686 Pull requests 246 Actions Projects Security and quality 75 Insights Additional navigation options Code Issue
04
Evidence and provenance
Published 10 Sept 2026 · Last source change 15 Sept 2026, 14:42 UTC · CWE-290 · Authentication Bypass by Spoofing
CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source FIRST · tracked since 2026-09-11
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2026-75584
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD enriched
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
- ENISA EUVD mappingEUVD-2026-75584 was added to the official ENISA EUVD mapping for this CVE.ENISA EUVD ↗
- Before
- not recorded
- After
- {"euvdId":"EUVD-2026-75584"}
- Vendor guidanceAuthoritative vendor guidance changed: added patch: github.com/0331801c72329e0eaeb850e53ccce87c57fbecf8; added patch: github.com/13720; 2 further additions.security-advisories@github.com ↗
- Before
- no authoritative guidance recorded
- After
- patch: github.com/0331801c72329e0eaeb850e53ccce87c57fbecf8 · patch: github.com/13720 · patch: github.com/GHSA-rf44-j88r-hh8c · 1 more references
- Affected versionsThe structured affected or fixed version information changed.CNA ↗
- Before
- < 2.11.56; >= 3.0.0, < 3.7.12 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
- After
- traefik: < 2.11.56, >= 3.0.0, < 3.7.12 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
- Remediation statusRemediation status changed from Awaiting fix to Patch available.security-advisories@github.com ↗
- Before
- Awaiting fix
- After
- Patch available
- Catalogue recordCVE added to the BlackTree catalogue.CNA ↗
Technical terms and abbreviations used in this report
- CVE
- Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
- CVSS
- Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
- EPSS
- Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
- CWE
- Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
- CNA
- CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
- CISA ADP
- Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
- NVD
- National Vulnerability Database: NIST's enrichment service for CVE records.
- CERT / CSIRT
- A computer security incident response team that publishes warnings or coordinates incident response.
- PoC
- Proof of concept: public material that demonstrates or helps reproduce exploitation.
- CSAF
- Common Security Advisory Framework: a machine-readable format for security advisories.
- LoTL
- Living off the land: abuse of legitimate tools or system functions during an attack.