CVE-2026-40611
Lego: Arbitrary File Write via Path Traversal in Webroot HTTP-01 Provider
CVSS Score
8.8
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-22 |
| Vendor | go-acme |
| Product | lego |
| Published | Apr 21, 2026 |
| Last Updated | Apr 21, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
Affected Versions
go-acme / lego
< 4.34.0