CVE-2026-40611

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.

PUBLISHED Reserved 2026-04-14 | Published 2026-04-21 | Updated 2026-04-21 | Assigner GitHub_M

Problem types

CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

Product status

References

github.com/...e/lego/security/advisories/GHSA-qqx8-2xmm-jrv8 exploit

github.com/...e/lego/security/advisories/GHSA-qqx8-2xmm-jrv8

cve.org (CVE-2026-40611)

nvd.nist.gov (CVE-2026-40611)

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