CVE-2026-40611
High · 8.8CVSS
8.8
EPSS
0.5%
Published
Apr 21, 2026
CISA due date
—
The record
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 packages
| Ecosystem | Package | Introduced | Fixed |
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