# CVE-2026-40611

> Vulnerability · severity: **HIGH** (CVSS 8.8).

## Description

Let's Encrypt client and ACME library written in Go (Lego). Prior to 4.34.0, the webroot HTTP-01 challenge provider in lego is vulnerable to arbitrary file write and deletion via path traversal. A malicious ACME server can supply a crafted challenge token containing ../ sequences, causing lego to write attacker-influenced content to any path writable by the lego process. This vulnerability is fixed in 4.34.0.

## Key facts

- **CVE ID:** CVE-2026-40611
- **Published:** 2026-04-21
- **CVSS severity:** HIGH
- **CVSS base score:** 8.8
- **CWE codes:** CWE-22

## Primary sources

- NIST NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40611

## Citation

> AI Analytics. CVE-2026-40611. Retrieved 2026-07-20 from https://api.ai-analytics.org/cve/CVE-2026-40611. Derived from NIST NVD. Licensed CC0.

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