CVE-2026-88008Network attack vector

Unauthenticated authorization bypass via forwarded h2c upgrade

Published Sep 10, 2026 · Updated Sep 10, 2026

Authorization bypass in Traefik Proxy 2.11.26 through 2.11.56 and 3.4.2 through 3.7.12 allows remote attackers to reach protected paths. Traefik forwards a client-supplied h2c upgrade and HTTP2-Settings to a shared backend, then converts a 101 response into a raw tunnel that bypasses routing and middleware for later HTTP/2 requests. Exploitation requires an unprotected route and a protected path on the same h2c-capable backend; later requests evade authentication, allowlists, rate limits, and telemetry.

CVSS severityUnavailable
Unscored
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authorization bypass in Traefik Proxy 2.11.26 through 2.11.56 and 3.4.2 through 3.7.12 allows remote attackers to reach protected paths. Traefik forwards a client-supplied h2c upgrade and HTTP2-Settings to a shared backend, then converts a 101 response into a raw tunnel that bypasses routing and middleware for later HTTP/2 requests. Exploitation requires an unprotected route and a protected path on the same h2c-capable backend; later requests evade authentication, allowlists, rate limits, and telemetry.

The record

CVE
CVE-2026-88008
Published
Sep 10, 2026
Updated
Sep 10, 2026
Vendor
Traefik Labs
Product
Traefik Proxy
Classifications
T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 10, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 10, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 2.11.26, < 2.11.57
  2. Affected versionversion=>= 3.4.2, < 3.7.13

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Traefik Labs · Traefik Proxyversion=>= 2.11.26, < 2.11.57; version=>= 3.4.2, < 3.7.13

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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