Caddy: MatchPath %xx (escaped-path) branch skips case normalization, enabling path-based route/auth bypass

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

7.7 · CVSS: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 · score source

EPSS

• CVE-2026-27587: 0.43% estimated exploitation activity in the next 30 days; percentile 36.80 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Caddy's HTTP path request matcher is intended to be case-insensitive, but when the match pattern contains percent-escape sequences (%xx) it compares against the request's escaped path without lowercasing. An attacker can bypass path-based routing and any access controls attached to that route by changing the casing of the request path. Details In Caddy v2.10.2, MatchPath is explicitly designed to be case-insensitive and lowercases match patterns during provisioning: - modules/caddyhttp/matchers.go: rationale captured in the MatchPath comment. - MatchPath.Provision lowercases configured patterns via strings.ToLower. - MatchPath.MatchWithError lowercases the request path for the normal matching path: reqPath := strings.ToLower(r.URL.Path). But when a match pattern contains a percent sign (%), MatchPath.MatchWithError switches to "escaped space" matching and builds the comparison string from r.URL.EscapedPath(): - reqPathForPattern := CleanPath(r.URL.EscapedPath(), mergeSlashes)…

Published by the source

24 Feb 2026, 20:31 UTC

Last modified by the source

27 Feb 2026, 19:53 UTC

Source last checked

26 Oct 2026, 15:14 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-g7pc-pc7g-h8jh

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# Patch Next advisory brief: CVE-2026-27587

Advisory: Caddy: MatchPath %xx (escaped-path) branch skips case normalization, enabling path-based route/auth bypass
IDs: CVE-2026-27587, GHSA-g7pc-pc7g-h8jh
Record: https://patchnext.com/advisories/cve-2026-27587 (revision 1, source checked 26 Oct 2026, 15:14 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/caddyserver/caddy/v2 2.11.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/caddyserver/caddy/v2: affected < 2.11.1; fixed in 2.11.1

## Suggested inspection (read-only)
- Go github.com/caddyserver/caddy/v2: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/caddyserver/caddy/v2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-g7pc-pc7g-h8jh (GitHub-reviewed advisory GHSA-g7pc-pc7g-h8jh lists affected ranges: Go github.com/caddyserver/caddy/v2 >=0 <2.11.1)

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