# CVE-2026-27585: Caddy's improper sanitization of glob characters in file matcher may lead to bypassing security protections

> Attackers can bypass path security protections in Caddy by exploiting unsanitized backslashes in file matchers, requiring specific configurations.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Feb 2026
- **Updated:** 26 Feb 2026
- **Also known as:** DEBIAN-CVE-2026-27585, GHSA-4xrr-hq4w-6vf4, GO-2026-4535, MINI-pccq-2pcm-jc44, UBUNTU-CVE-2026-27585

## What is CVE-2026-27585?

CVE-2026-27585 is a medium-severity path traversal vulnerability in caddyserver caddy, published on 24 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, the path sanitization routine in file matcher doesn't sanitize backslashes which can lead to bypassing path related security protections. It affects users with specific Caddy and environment configurations. Version 2.11.1 fixes the issue.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-27585?

3 open source packages ship an affected version, including github.com/caddyserver/caddy/v2. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/caddyserver/caddy/v2` | Go | All versions | 2.11.1 |
| `github.com/caddyserver/caddy/v2` | Go | All versions | 2.11.1 |
| `github.com/caddyserver/caddy/v2` | Go | All versions | 2.11.1 |

Products: Caddyserver Caddy.

## How do I fix CVE-2026-27585?

Upgrade github.com/caddyserver/caddy/v2 to 2.11.1 or later.

## Is CVE-2026-27585 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27585 exists.

## Other vulnerabilities in caddyserver caddy

- [CVE-2018-21246](https://insights.sbomify.com/CVE-2018-21246/): Caddy vulnerable to Authentication Bypass due to mishandling of TLS client authentication (critical 9.8)
- [CVE-2026-27590](https://insights.sbomify.com/CVE-2026-27590/): Caddy: Unicode case-folding length expansion causes incorrect split_path index in FastCGI transport (high 8.9)
- [CVE-2026-27586](https://insights.sbomify.com/CVE-2026-27586/): Caddy's mTLS client authentication silently fails open when CA certificate file is missing or malformed (high 8.8)
- [CVE-2026-45135](https://insights.sbomify.com/CVE-2026-45135/): Caddy: Unsafe Unicode Handling in FastCGI splitPos Allows Execution of Non-PHP Files (high 8.1)
- [CVE-2026-52845](https://insights.sbomify.com/CVE-2026-52845/): Caddy: FastCGI header normalization bypass in `forward_auth copy_headers` (high 8.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-27585 and fix it if it is affected.

What it is: CVE-2026-27585 is a medium-severity path traversal vulnerability in caddyserver caddy, published on 24 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27585 exists.

Affected packages and fixed versions:
- github.com/caddyserver/caddy/v2 (Go): affected all versions; fixed in 2.11.1
- github.com/caddyserver/caddy/v2 (Go): affected all versions; fixed in 2.11.1
- github.com/caddyserver/caddy/v2 (Go): affected all versions; fixed in 2.11.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-27585/ (Markdown: https://insights.sbomify.com/CVE-2026-27585/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27585
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27585
- OSV: https://osv.dev/vulnerability/CVE-2026-27585

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-27585/
Summaries are generated and may contain mistakes; the official description above is the record.