What is CVE-2026-40611?

CVE-2026-40611 is a high-severity vulnerability in Go-acme Lego, classified under Path Traversal. CVSS score: 8.8/10. Published 2026-04-21.

How severe is CVE-2026-40611?

High severity. CVSS v3 base score is 8.8 out of 10.

Path Traversal in Go-acme Lego

CVE-2026-40611

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…

Vulnerability class: Path Traversal (Directory Traversal)

EPSS: 0.001 (17.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

Affected products

Go-acme Lego — versions < 4.34.0

Weakness classification (CWE)

CWE-22 — Path Traversal

References

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

Frequently asked questions

What is CVE-2026-40611?: CVE-2026-40611 is a high-severity vulnerability in Go-acme Lego, classified under Path Traversal. CVSS score: 8.8/10. Published 2026-04-21.
How severe is CVE-2026-40611?: High severity. CVSS v3 base score is 8.8 out of 10.