Path traversal in lego - CVE-2026-40611
Published: April 16, 2026
Vulnerability identifier: #VU126357
CSH Severity: High
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
CVE-ID: CVE-2026-40611
CWE-ID: CWE-22
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: go-acme
Affected software:
lego
lego
Detailed vulnerability description
The vulnerability allows a remote attacker to write or delete arbitrary files.
The vulnerability exists due to path traversal in the webroot HTTP-01 challenge provider when processing a crafted ACME challenge token. A remote attacker can supply a token containing traversal sequences to write or delete arbitrary files.
User interaction is required to run lego against a malicious or compromised ACME server with the HTTP-01 webroot challenge solver enabled.
How to mitigate CVE-2026-40611
Install security update from vendor's website.