Evidence used
- No CISA KEV confirmation is currently recorded.
- A structured source references public exploit or proof-of-concept material.
- EPSS is 0.56% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2026
CVE-2026-33433High confidence
Traefik Vulnerable to BasicAuth/DigestAuth Identity Spoofing via Non-Canonical headerField
traefik · traefik
Official source article: GitHub GHSA-QR99-7898-VR7C ↗. Check the applicable product and release in the original source.
5.1MediumCVSS 4.0
Within 7 days
Patch availableMedium technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityMedium→Operational priority:High, raised one band.upgradedsince 15 Jul 2026
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict the affected network interface to trusted sources where business-safe.
- Increase monitoring for the attack path and post-exploitation behaviour described in the report.
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.
Open-source package ranges6 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 | SEMVER: introduced 0; fixed 2.11.42 | 2.11.42 | OSV record ↗aggregator derived · 10 Sep 2026 |
| Gogithub.com/traefik/traefik/v3 | SEMVER: introduced 3.0.0-beta1; fixed 3.6.12 | 3.6.12 | OSV record ↗aggregator derived · 10 Sep 2026 |
| Gogithub.com/traefik/traefik/v3 | SEMVER: introduced 3.7.0-ea.1; fixed 3.7.0-ea.3 | 3.7.0-ea.3 | OSV record ↗aggregator derived · 10 Sep 2026 |
| gogithub.com/traefik/traefik/v2 | < 2.11.42 | 2.11.42 | GitHub advisory ↗upstream repository advisory · 27 Mar 2026 |
| gogithub.com/traefik/traefik/v3 | >= 3.0.0-beta1, < 3.6.11 | 3.6.12 | GitHub advisory ↗upstream repository advisory · 27 Mar 2026 |
| gogithub.com/traefik/traefik/v3 | >= 3.7.0-ea.1, < 3.7.0-ea.3 | 3.7.0-ea.3 | GitHub advisory ↗upstream repository advisory · 27 Mar 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-2026-33433 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitygithub.com/traefik/traefik: Traefik: Authentication bypass via non-canonical HTTP header injection
The vendor explicitly identifies these products or versions as containing the fix.
- registry.redhat.io/devspaces/traefik-rhel9@sha256:179efd9379165b0e7992d0cca5e2c94cb25412153ea333e4c01d693bf64ad736_amd64 as a component of Red Hat OpenShift Dev Spaces 3.27
- registry.redhat.io/devspaces/traefik-rhel9@sha256:34f8243809fb492094eb221362addaa91ab8d2dd9f233383328b695bc1f559c4_arm64 as a component of Red Hat OpenShift Dev Spaces 3.27
- registry.redhat.io/devspaces/traefik-rhel9@sha256:cbf71be94cfa5f2eaee079395261f3130b8857f38f210f5732280d30a792492c_s390x as a component of Red Hat OpenShift Dev Spaces 3.27
- registry.redhat.io/devspaces/traefik-rhel9@sha256:ee3f68c28619e2af980739a351305c843d0ebb8bc98bda61e77cfabbb2e11641_ppc64le as a component of Red Hat OpenShift Dev Spaces 3.27
- Summary
- A flaw was found in Traefik, an HTTP reverse proxy and load balancer. When the `headerField` is configured with a non-canonical HTTP header name, an authenticated attacker can inject a canonical version of that header. This allows the attacker to impersonate any identity to the backend, leading to an authentication bypass. The backend prioritizes the attacker-injected header, overriding Traefik's intended header.
- Remediation
- Before applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
Medium technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.
Patch available01
What, why and how
Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.42, 3.6.11, and 3.7.0-ea.3, when `headerField` is configured with a non-canonical HTTP header name (e.g., `x-auth-user` instead of `X-Auth-User`), an authenticated attacker can inject their own canonical version of that header to impersonate any identity to the backend. The backend receives two header entries — the attacker-injected canonical one is read first, overriding Traefik's non-canonical write. Versions 2.11.42, 3.6.11, and 3.7.0-ea.3 patch the issue.
What
Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.42, 3.6.11, and 3.7.0-ea.3, when `headerField` is configured with a non-canonical HTTP header name (e.g., `x-auth-user` instead of `X-Auth-User`), an authenticated attacker can inject their own canonical version of that header to impersonate any identity to the backend. The backend receives two header entries — the attacker-injected canonical one is read first, overriding Traefik's non-canonical write. Versions 2.11.42, 3.6.11, and 3.7.0-ea.3 patch the issue.
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 elevated privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.42, 3.6.11, and 3.7.0-ea.3, when `headerField` is configured with a non-canonical HTTP header name (e.g., `x-auth-user` instead of `X-Auth-User`), an authenticated attacker can inject their own canonical version of that header to impersonate any identity to the backend. The backend receives two header entries — the attacker-injected canonical one is read first, overriding Traefik's non-canonical write. Versions 2.11.42, 3.6.11, and 3.7.0-ea.3 patch the issue.
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 elevated 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 Reference recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.A structured CVE source labels at least one public reference as exploit material. BlackTree has not independently validated that it is safe, reliable or weaponised.
- 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
- High: elevated access is required
- User interaction
- None
- Attack complexity
- High: exploitation depends on specific conditions
- 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:H/AT:P/PR:H/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.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.ATPresentAttack requirements: A particular deployment or execution condition must be present.PRHighPrivileges required: The attacker needs elevated or administrative 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. - Patch available
- Fixed
- registry.redhat.io/devspaces/traefik-rhel9@sha256:179efd9379165b0e7992d0cca5e2c94cb25412153ea333e4c01d693bf64ad736_amd64 as a component of Red Hat OpenShift Dev Spaces 3.27
- registry.redhat.io/devspaces/traefik-rhel9@sha256:34f8243809fb492094eb221362addaa91ab8d2dd9f233383328b695bc1f559c4_arm64 as a component of Red Hat OpenShift Dev Spaces 3.27
- registry.redhat.io/devspaces/traefik-rhel9@sha256:cbf71be94cfa5f2eaee079395261f3130b8857f38f210f5732280d30a792492c_s390x as a component of Red Hat OpenShift Dev Spaces 3.27
- registry.redhat.io/devspaces/traefik-rhel9@sha256:ee3f68c28619e2af980739a351305c843d0ebb8bc98bda61e77cfabbb2e11641_ppc64le as a component of Red Hat OpenShift Dev Spaces 3.27
- Action
- Before applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
- Workaround
- No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04
Evidence and provenance
Published 27 Mar 2026 · Last source change 15 Jul 2026, 01:06 UTC · CWE-290 · Authentication Bypass by Spoofing
CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source FIRST · tracked since 2026-08-14
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2026-16616
Product sourceCNA
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD modified after enrichment
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
- Affected versionsThe structured affected or fixed version information changed.Red Hat Product Security ↗
- Before
- < 2.11.42; >= 3.0.0-beta1, < 3.6.11; >= 3.7.0-ea.1, < 3.7.0-ea.3 · 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.
- After
- < 2.11.42; >= 3.0.0-beta1, < 3.6.11; >= 3.7.0-ea.1, < 3.7.0-ea.3 · Fixed: Before applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
CVE published
Fixed release or patch reference recorded
Fixed release recorded from official guidance
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.