CVE-2026-40611Lego: Arbitrary File Write via Path Traversal in Webroot HTTP-01 Provider

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.

Data: CVE.org, NVD, CISA KEV, FIRST EPSS, Ubuntu. Published as the sources state it, in English.

Affected products and versions

References and patches

• https://github.com/go-acme/lego/security/advisories/GHSA-qqx8-2xmm-jrv8
• https://access.redhat.com/errata/RHSA-2026:21772
• https://access.redhat.com/security/cve/CVE-2026-40611
• https://bugzilla.redhat.com/show_bug.cgi?id=2460233
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40611.json