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NVD / CVE Program· CNA GitHub_M

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

Noroxi assessment

Priority: Monitor (action score 20/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.48% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. Administrator privileges are required. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: github.com/traefik/traefik/v2 (Go) 2.11.42; github.com/traefik/traefik/v3 (Go) 3.6.12, 3.7.0-ea.3; govulncheck-vulndb (openSUSE:Leap 15.6) 0.0.20260402T184258-150000.1.158.1.

Low priority for now. Upgrade to github.com/traefik/traefik/v2 (Go) 2.11.42; github.com/traefik/traefik/v3 (Go) 3.6.12, 3.7.0-ea.3; govulncheck-vulndb (openSUSE:Leap 15.6) 0.0.20260402T184258-150000.1.158.1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

MediumCVSS 5.1 · v4.0—No exploit Fix available
Published
Mar 27, 2026
Updated
Jul 15, 2026
EPSS
0.4% · 41th percentile

Report tools

JSON

Action score

20

Monitor

Low priority for now.

CVSS
20 / 40 · 5.1 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_M
5.1
NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-33433

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
traefiktraefik

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • traefik traefikbefore 2.11.42
  • traefik traefik3.0.0 and later · before 3.6.12
  • traefik traefik3.7.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • traefik traefik

    • < 2.11.42, >= 3.0.0-beta1, < 3.6.11, >= 3.7.0-ea.1, < 3.7.0-ea.3affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Gogithub.com/traefik/traefikfrom 0—
Gogithub.com/traefik/traefik/v2before 2.11.422.11.42
Gogithub.com/traefik/traefik/v3from 3.0.0-beta1 · before 3.6.123.6.12
Gogithub.com/traefik/traefik/v3from 3.7.0-ea.1 · before 3.7.0-ea.33.7.0-ea.3
openSUSE:Leap 15.6govulncheck-vulndbbefore 0.0.20260402T184258-150000.1.158.10.0.20260402T184258-150000.1.158.1

Same product

traefik: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-85595Traefik before v2.11.55 and v3.0.0 through v3.7.10 Authentication Bypass via digestAuth
    38Monitor
  • CVE-2026-88877Traefik v3.7.0 Authentication Bypass via from-to-www-redirect
    37Monitor
  • CVE-2026-88007Traefik HTTP/3 Backend NTLM Connection Reuse
    36Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-32595Mar 20, 2026 · Traefik: BasicAuth Middleware Timing Attack Allows Username Enumeration
    25Monitor
  • ← EarlierCVE-2026-32695Mar 27, 2026 · Traefik has Knative Ingress Rule Injection that Allows Host Restriction Bypass
    25Monitor
  • Later →CVE-2026-35051Apr 30, 2026 · Traefik: ForwardAuth trustForwardHeader=false allows spoofed X-Forwarded-Prefix to bypass auth
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Go:github.com/traefik/traefik/v22.11.42Package registry (OSV)
Go:github.com/traefik/traefik/v33.6.12Package registry (OSV)
Go:github.com/traefik/traefik/v33.7.0-ea.3Package registry (OSV)
opensuse:govulncheck-vulndb0.0.20260402T184258-150000.1.158.1 · openSUSE:Leap 15.6Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-3985834 days apartTraefik: Forwarded alias spoofing top pre-auth decision bypass
    31Monitor
  • CVE-2026-114640209 days apartTraefik v3.7.0 before v3.7.14 mTLS Header Spoofing via Ingress-NGINX HTTP Router
    28Monitor
  • CVE-2026-88011167 days apartTraefik: ForwardAuth identity spoofing via dot-form header alias
    21Monitor
  • CVE-2026-88879167 days apartTraefik before v2.11.56 Identity Spoofing via Header Alias
    21Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • Administrator privileges are required.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
High
Privileges required
High
User interaction
None
Scope
X

Weakness class (CWE)

CWE-290 · Authentication Bypass by Spoofing

CVSS 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. Fix✗ → ✓

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References

Show all references (6 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records