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CVE Record

CVE-2026-33433: Traefik Vulnerable to BasicAuth/DigestAuth Identity Spoofing via Non-Canonical headerField

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.

HighCVSS 7.7Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2026-33433 lets an authenticated attacker spoof the user identity Traefik forwards to backend services, but only under a specific configuration. If BasicAuth or DigestAuth uses a non-canonical headerField, a backend may trust the attacker-controlled identity header first. Patched Traefik versions are available.

Executive priority

Prioritize this for internet-facing or shared Traefik environments where backend apps trust Traefik-provided identity headers. The issue is high severity but configuration-dependent, so rapid inventory and targeted patching are appropriate.

Technical view

Affected Traefik versions mishandle BasicAuth/DigestAuth headerField when the configured header name is non-canonical. A canonical duplicate header supplied by an authenticated attacker can be processed before Traefik's written header, causing backend identity confusion. CVSS is 7.7 high with high confidentiality and integrity impact.

Likely exposure

Likely exposure is Traefik deployments before 2.11.42, 3.6.11, or 3.7.0-ea.3 that use BasicAuth or DigestAuth with headerField configured using non-canonical casing. Risk is highest where backend applications trust that forwarded identity header for authorization or audit decisions.

Exploitation context

The provided sources do not show CISA KEV listing or active exploitation. Exploitation is conditional: the attacker must be authenticated and the vulnerable headerField configuration must exist. If present, impact can include impersonation and backend authorization bypass.

Researcher notes

Focus analysis on header canonicalization and duplicate-header handling between Traefik middleware and backend frameworks. Evidence supports identity spoofing only when headerField is non-canonical; do not generalize this to all Traefik authentication deployments.

Mitigation direction

  • Upgrade Traefik to 2.11.42, 3.6.11, 3.7.0-ea.3, or later.
  • Review Red Hat advisory RHSA-2026:10175 for distribution package status.
  • Check vendor guidance before relying on compensating controls.
  • Temporarily reduce trust in forwarded identity headers until patched.

Validation and detection

  • Inventory Traefik versions and compare them with affected ranges.
  • Review BasicAuth and DigestAuth configurations for headerField usage.
  • Identify backend services that trust forwarded identity headers.
  • Confirm remediation by verifying Traefik runs a patched version.
Prepared
Confidence
high
Sources
8

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-290: Exact CWE lookup

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cve · low confidence lookup

CVE-2026-33433 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.7 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
9Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.7CVSS 3.1HighCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:N1.35.8redhat-SADP
5.1CVSS 4.0MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N——GitHub_M

Vulnerability scoring details

Base CVSS 4.0 score

5.1Medium
CVSS 4.0 vector shape for CVE-2026-33433Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPgithub.com/traefik/traefik: Traefik: Authentication bypass via non-canonical HTTP header injection
other:Red Hat severity ratingcvssV3_1
  • 2026-03-27T15:03:19.672Z: Reported to Red Hat.
  • 2026-03-27T13:49:08.455Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
traefiktraefik< 2.11.42, >= 3.0.0-beta1, < 3.6.11, >= 3.7.0-ea.1, < 3.7.0-ea.3Listed
Weakness

CWE details

CWE-290

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-290 · source CWE mapping

Authentication Bypass by Spoofing

Authentication Bypass by Spoofing represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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