CVE-2026-27587Public exploitNetwork attack vector

Unauthenticated route bypass via escaped-path case mismatch

Published Feb 24, 2026 · Updated Feb 24, 2026

Improper case handling in Caddy before 2.11.1 allows remote attackers to bypass path-based routing via mixed-case escaped paths. MatchPath.MatchWithError lowercases the ordinary request path but passes r.URL.EscapedPath() through CleanPath without lowercasing when a configured pattern contains %xx. Exploitation requires such a path matcher and a downstream route that accepts the differently cased path, causing the protected request to reach an unauthorized handler.

CVSS severity9.1
Critical
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper case handling in Caddy before 2.11.1 allows remote attackers to bypass path-based routing via mixed-case escaped paths. MatchPath.MatchWithError lowercases the ordinary request path but passes r.URL.EscapedPath() through CleanPath without lowercasing when a configured pattern contains %xx. Exploitation requires such a path matcher and a downstream route that accepts the differently cased path, causing the protected request to reach an unauthorized handler.

The record

CVE
CVE-2026-27587
Published
Feb 24, 2026
Updated
Feb 24, 2026
Vendor
Caddy
Product
Caddy
Classifications
CWE-178, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 24, 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=< 2.11.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Caddy · Caddyversion=< 2.11.1

Published CVSS scores

7.7GitHubCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P
9.1NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

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.

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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 exploitPublished

Weakness, pattern, technique

CWE-178Improper Handling of Case Sensitivity
T1190Exploit Public-Facing Application

Public exploit references

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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