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Full vulnerability report · 2026
CVE-2026-53622High confidence

Traefik: HTTP/3 mTLS bypass via exact SNI TLSOptions lookup for wildcard and mixed-case hosts

traefik · traefik

Official source article: GitHub GHSA-9CR8-Q42Q-G8M7 ↗. Check the applicable product and release in the original source.

7.8HighCVSS 4.0
Recommended action
Within 7 days

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:Critical, raised one band.upgradedsince 2 Sep 2026

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • A structured source references public exploit or proof-of-concept material.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 0.63% for the current model date.

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

  1. Confirm that the asset runs traefik traefik and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Open-source package ranges8 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 packageAffected rangeFirst fixed versionEvidence
Gogithub.com/traefik/traefikSEMVER: introduced 0; last affected 1.7.34Not statedOSV record ↗aggregator derived · 10 Sep 2026
Gogithub.com/traefik/traefik/v2SEMVER: introduced 0; fixed 2.11.512.11.51OSV record ↗aggregator derived · 10 Sep 2026
Gogithub.com/traefik/traefik/v3SEMVER: introduced 3.7.0; fixed 3.7.33.7.3OSV record ↗aggregator derived · 10 Sep 2026
Gogithub.com/traefik/traefik/v3SEMVER: introduced 0; fixed 3.6.183.6.18OSV record ↗aggregator derived · 10 Sep 2026
gogithub.com/traefik/traefik<= 1.7.34Not statedGitHub advisory ↗upstream repository advisory · 2 Sep 2026
gogithub.com/traefik/traefik/v2<= 2.11.502.11.51GitHub advisory ↗upstream repository advisory · 2 Sep 2026
gogithub.com/traefik/traefik/v3>= 3.7.0, <= 3.7.23.7.3GitHub advisory ↗upstream repository advisory · 2 Sep 2026
gogithub.com/traefik/traefik/v3<= 3.6.173.6.18GitHub advisory ↗upstream repository advisory · 2 Sep 2026
Direct vendor intelligence

Authoritative 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.

1 current
CVE-2026-53622 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitygithub.com/traefik/traefik: Traefik: mTLS enforcement bypass due to HTTP/3 TLS configuration flaw
4 fixed

The vendor explicitly identifies these products or versions as containing the fix.

  • registry.redhat.io/devspaces/traefik-rhel9@sha256:38a0acf8e97a7d0c6a4c8d6815321e35df6ad35736a7338267ce9b5adb118662_amd64 as a component of Red Hat OpenShift Dev Spaces 3.30
  • registry.redhat.io/devspaces/traefik-rhel9@sha256:8b8f3387a3764beb3d8ad6a027b05f42619ccf33165e733e8dc7b3f135895dc5_ppc64le as a component of Red Hat OpenShift Dev Spaces 3.30
  • registry.redhat.io/devspaces/traefik-rhel9@sha256:b338c1060dd859a8747e0812e176ab266d338aea799becd41e48afc50061fb82_s390x as a component of Red Hat OpenShift Dev Spaces 3.30
  • registry.redhat.io/devspaces/traefik-rhel9@sha256:ba0aebd6b6b6ceb676b6990d5bd9f3b7efe40cedd9407149da92c55435ef7db6_arm64 as a component of Red Hat OpenShift Dev Spaces 3.30
Summary
A flaw was found in Traefik, an HTTP reverse proxy and load balancer. This critical vulnerability in Traefik's HTTP/3 (QUIC) TLS configuration selection allows unauthenticated clients to bypass router-specific mutual Transport Layer Security (mTLS) enforcement. When HTTP/3 is enabled and a router uses wildcard host rules or case-insensitive hostname matching with client certificate authentication, an attacker can complete the QUIC handshake without presenting a certificate. This bypass grants unauthorized access to a backend that should be protected by mTLS.
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
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-38576

No EUVD known-exploited evidence

Traefik is an HTTP reverse proxy and load balancer. Versions prior to 3.7.3, 3.6.18, and 2.11.51 have a critical vulnerability in Traefik's HTTP/3 (QUIC) TLS configuration selection that allows unauthenticated clients to bypass router-specific mTLS enforcement. When HTTP/3 is enabled on an entrypoint, the TLS handshake selects the applicable TLS configuration through an exact, case-sensitive lookup on the SNI value, which fails to match wildcard host patterns (e.g., *.example.com) or case variants of the configured hostname. Because the handshake falls back to the default TLS configuration — which may not require client certificates — a client can complete the QUIC handshake without presenting a certificate, while the subsequent HTTP routing layer still dispatches the request to a backend protected by a router-specific mTLS policy. The issue affects deployments where HTTP/3 is enabled, a router uses a wildcard Host rule or case-insensitive hostname matching, a router-specific TLSOptions enforces client certificate authentication, and UDP access to the entrypoint is reachable by an attacker. This vulnerability is fixed in versions 3.7.3, 3.6.18, and 2.11.51.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
7.8 · CVSS 4.0
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

Traefik is an HTTP reverse proxy and load balancer. Versions prior to 3.7.3, 3.6.18, and 2.11.51 have a critical vulnerability in Traefik's HTTP/3 (QUIC) TLS configuration selection that allows unauthenticated clients to bypass router-specific mTLS enforcement. When HTTP/3 is enabled on an entrypoint, the TLS handshake selects the applicable TLS configuration through an exact, case-sensitive lookup on the SNI value, which fails to match wildcard host patterns (e.g., *.example.com) or case variants of the configured hostname. Because the handshake falls back to the default TLS configuration — which may not require client certificates — a client can complete the QUIC handshake without presenting a certificate, while the subsequent HTTP routing layer still dispatches the request to a backend protected by a router-specific mTLS policy. The issue affects deployments where HTTP/3 is enabled, a router uses a wildcard Host rule or case-insensitive hostname matching, a router-specific TLSOptions enforces client certificate authentication, and UDP access to the entrypoint is reachable by an attacker. This vulnerability is fixed in versions 3.7.3, 3.6.18, and 2.11.51.

What

Traefik is an HTTP reverse proxy and load balancer. Versions prior to 3.7.3, 3.6.18, and 2.11.51 have a critical vulnerability in Traefik's HTTP/3 (QUIC) TLS configuration selection that allows unauthenticated clients to bypass router-specific mTLS enforcement. When HTTP/3 is enabled on an entrypoint, the TLS handshake selects the applicable TLS configuration through an exact, case-sensitive lookup on the SNI value, which fails to match wildcard host patterns (e.g., *.example.com) or case variants of the configured hostname. Because the handshake falls back to the default TLS configuration — which may not require client certificates — a client can complete the QUIC handshake without presenting a certificate, while the subsequent HTTP routing layer still dispatches the request to a backend protected by a router-specific mTLS policy. The issue affects deployments where HTTP/3 is enabled, a router uses a wildcard Host rule or case-insensitive hostname matching, a router-specific TLSOptions enforces client certificate authentication, and UDP access to the entrypoint is reachable by an attacker. This vulnerability is fixed in versions 3.7.3, 3.6.18, and 2.11.51.

Why

The product requires authentication, but the product has an alternate path or channel that does not require authentication.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. 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. Versions prior to 3.7.3, 3.6.18, and 2.11.51 have a critical vulnerability in Traefik's HTTP/3 (QUIC) TLS configuration selection that allows unauthenticated clients to bypass router-specific mTLS enforcement. When HTTP/3 is enabled on an entrypoint, the TLS handshake selects the applicable TLS configuration through an exact, case-sensitive lookup on the SNI value, which fails to match wildcard host patterns (e.g., *.example.com) or case variants of the configured hostname. Because the handshake falls back to the default TLS configuration — which may not require client certificates — a client can complete the QUIC handshake without presenting a certificate, while the subsequent HTTP routing layer still dispatches the request to a backend protected by a router-specific mTLS policy. The issue affects deployments where HTTP/3 is enabled, a router uses a wildcard Host rule or case-insensitive hostname matching, a router-specific TLSOptions enforces client certificate authentication, and UDP access to the entrypoint is reachable by an attacker. This vulnerability is fixed in versions 3.7.3, 3.6.18, and 2.11.51.

Why

The product requires authentication, but the product has an alternate path or channel that does not require authentication.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. 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
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

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
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Reference recorded

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 Using an Alternate Path or Channel → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
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-288 ↗

CWE-288: Authentication Bypass Using an Alternate Path or Channel. The product requires authentication, but the product has an alternate path or channel that does not require authentication.

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:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N

Common 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.ATNoneAttack requirements: No additional deployment or execution condition is required.PRNonePrivileges required: The attacker does not need an account or existing 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.
NetworkUnauthenticatedCWE-288Public exploit reference
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-38576Official EUVD mapping

Traefik is an HTTP reverse proxy and load balancer. Versions prior to 3.7.3, 3.6.18, and 2.11.51 have a critical vulnerability in Traefik's HTTP/3 (QUIC) TLS configuration selection that allows unauthenticated clients to bypass router-specific mTLS enforcement. When HTTP/3 is enabled on an entrypoint, the TLS handshake selects the applicable TLS configuration through an exact, case-sensitive lookup on the SNI value, which fails to match wildcard host patterns (e.g., *.example.com) or case variants of the configured hostname. Because the handshake falls back to the default TLS configuration — which may not require client certificates — a client can complete the QUIC handshake without presenting a certificate, while the subsequent HTTP routing layer still dispatches the request to a backend protected by a router-specific mTLS policy. The issue affects deployments where HTTP/3 is enabled, a router uses a wildcard Host rule or case-insensitive hostname matching, a router-specific TLSOptions enforces client certificate authentication, and UDP access to the entrypoint is reachable by an attacker. This vulnerability is fixed in versions 3.7.3, 3.6.18, and 2.11.51.

Official EUVD record ↗
Cyber Security Agency of Singapore · English · CSA-SB-20260624Security Bulletin 24 June 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 24 June 2026, published on 24 June 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-021262traefikにおける代替パスまたはチャネルを使用した認証回避に関する脆弱性

TraefikはHTTPリバースプロキシおよびロードバランサーです。バージョン3.7.3以前には、TraefikのHTTP/3（QUIC）TLS構成選択に重大な脆弱性が存在していました。この脆弱性により、認証されていないクライアントがルーター固有のmTLS強制を回避できる可能性があります。HTTP/3がエントリポイントで有効になっている場合、TLSハンドシェイクはSNI値の正確で大文字・小文字を区別する検索を通じて適用されるTLS構成を選択しますが、これによりワイルドカードホストパターン（例：*.example.com）や設定されたホスト名の大文字小文字のバリエーションとマッチしません。ハンドシェイクがデフォルトのTLS構成にフォールバックするため（クライアント証明書を要求しない場合があります）、クライアントは証明書を提示せずにQUICハンドシェイクを完了でき、その後のHTTPルーティング層でルーター固有のmTLSポリシーで保護されたバックエンドにリクエストをディスパッチします。この問題は、HTTP/3が有効で、ルーターがワイルドカードホストルールまたは大文字小文字を区別しないホスト名のマッチングを使用し、ルーター固有のTLSOptionsがクライアント証明書認証を強制し、攻撃者がエントリポイントへのUDPアクセスが可能な環境に影響します。この脆弱性はバージョン3.7.3で修正されました。

Official advisory ↗
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
Affected
traefik: 3.7.0, < 3.7.3, 3.0.0, < 3.6.18, < 2.11.51
Fixed
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
A mitigation or workaround reference is available from the source linked below; validate it against the affected product and version.
04

Evidence and provenance

Published 23 Jun 2026 · Last source change 2 Sept 2026, 12:04 UTC · CWE-288 · Authentication Bypass Using an Alternate Path or Channel

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-38576
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

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    traefik: < 3.7.3 · 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
    traefik: >= 3.7.0, < 3.7.3, >= 3.0.0, < 3.6.18, < 2.11.51 · Fixed: RHSA-2026:62260: Red Hat OpenShift Dev Spaces 3.30
    CNA ↗
  2. Vendor guidanceAuthoritative vendor guidance changed: removed vendor advisory: access.redhat.com/RHSA-2026:62260.
    Before
    patch: github.com/GHSA-9cr8-q42q-g8m7 · patch: github.com/v3.7.3 · remediation: github.com/GHSA-9cr8-q42q-g8m7 · 1 more references
    After
    patch: github.com/GHSA-9cr8-q42q-g8m7 · patch: github.com/v3.7.3 · remediation: github.com/GHSA-9cr8-q42q-g8m7
    security-advisories@github.com ↗
  3. Vendor guidanceAuthoritative vendor guidance changed: added vendor advisory: access.redhat.com/RHSA-2026:62260.
    Before
    patch: github.com/GHSA-9cr8-q42q-g8m7 · patch: github.com/v3.7.3 · remediation: github.com/GHSA-9cr8-q42q-g8m7
    After
    patch: github.com/GHSA-9cr8-q42q-g8m7 · patch: github.com/v3.7.3 · remediation: github.com/GHSA-9cr8-q42q-g8m7 · 1 more references
    security-advisories@github.com ↗
  4. Affected versionsThe structured affected or fixed version information changed.
    Before
    < 3.7.3 · 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
    >= 3.7.0, < 3.7.3; >= 3.0.0, < 3.6.18; < 2.11.51 · 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.
    CNA ↗
  5. Affected versionsThe structured affected or fixed version information changed.
    Before
    >= 3.7.0, < 3.7.3; >= 3.0.0, < 3.6.18; < 2.11.51 · 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
    traefik: < 3.7.3 · 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.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2026-38576↗Vendor CSAF · Red Hat Product Security↗Public exploit reference · GitHub GHSA-9CR8-Q42Q-G8M7↗Patch or update reference↗Official CVE record (CNA and ADP data)↗NVD record↗
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.
Free version - for non-commercial use only.CVE-2026-53622 · cve.blacktree.nl