CVE-2026-40611: CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') in go-acme lego
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.
AI Analysis
Technical Summary
The go-acme lego client, used for Let's Encrypt ACME challenges, contains a path traversal vulnerability (CWE-22) in its webroot HTTP-01 challenge provider prior to version 4.34.0. An attacker controlling an ACME server can craft challenge tokens containing '../' sequences that cause the lego client to write or delete files outside the intended directory, anywhere writable by the lego process. This can lead to arbitrary file write and deletion, impacting confidentiality, integrity, and availability. The issue is resolved in lego version 4.34.0.
Potential Impact
Successful exploitation allows an attacker controlling an ACME server to write or delete arbitrary files on the system where lego runs, limited to paths writable by the lego process. This can lead to full compromise of the affected system's data confidentiality, integrity, and availability. The CVSS score of 8.8 reflects the high impact and network attack vector with no privileges required but user interaction needed.
Mitigation Recommendations
Upgrade the go-acme lego client to version 4.34.0 or later, where this path traversal vulnerability is fixed. No other mitigations are specified. Patch status is confirmed fixed in 4.34.0.
CVE-2026-40611: CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') in go-acme lego
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.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The go-acme lego client, used for Let's Encrypt ACME challenges, contains a path traversal vulnerability (CWE-22) in its webroot HTTP-01 challenge provider prior to version 4.34.0. An attacker controlling an ACME server can craft challenge tokens containing '../' sequences that cause the lego client to write or delete files outside the intended directory, anywhere writable by the lego process. This can lead to arbitrary file write and deletion, impacting confidentiality, integrity, and availability. The issue is resolved in lego version 4.34.0.
Potential Impact
Successful exploitation allows an attacker controlling an ACME server to write or delete arbitrary files on the system where lego runs, limited to paths writable by the lego process. This can lead to full compromise of the affected system's data confidentiality, integrity, and availability. The CVSS score of 8.8 reflects the high impact and network attack vector with no privileges required but user interaction needed.
Mitigation Recommendations
Upgrade the go-acme lego client to version 4.34.0 or later, where this path traversal vulnerability is fixed. No other mitigations are specified. Patch status is confirmed fixed in 4.34.0.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-04-14T14:07:59.642Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69e7bb7219fe3cd2cdedac91
Added to database: 4/21/2026, 6:01:22 PM
Last enriched: 4/21/2026, 6:16:04 PM
Last updated: 4/21/2026, 7:56:57 PM
Views: 5
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