CVE-2026-40611

About vulnerability

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.

Affected product:

Loki , caddyserver/caddy , caddyserver/certmagic , coredns/coredns , go-acme/lego , hashicorp/consul , influxdata/telegraf

Affected packages:

github.com/hashicorp/consul @ 1.14.5 (+8 more)

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.