CVE-2026-40611

high

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.

References

https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40611.json

https://github.com/go-acme/lego/security/advisories/GHSA-qqx8-2xmm-jrv8

https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-24219

https://bugzilla.redhat.com/show_bug.cgi?id=2460233

https://access.redhat.com/security/cve/CVE-2026-40611

https://access.redhat.com/errata/RHSA-2026:21772

Details

Source: Mitre, NVD

Published: 2026-04-21

Updated: 2026-07-15

Named Vulnerability: GO-2026-5593Named Vulnerability: GHSA-qqx8-2xmm-jrv8

Risk Information

CVSS v2

Base Score: 10

Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:C

Severity: Critical

CVSS v3

Base Score: 8.8

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Severity: High

EPSS

EPSS: 0.00546