CVE-2026-48126 Details
Description
Algernon is a small self-contained pure-Go web server. Prior to 1.17.8, when algernon is started with --domain (or --letsencrypt, which silently turns on --domain at engine/flags.go:372), the request handler resolves the served directory by joining the configured --dir with the value of the client-supplied Host header. The join is performed by filepath.Join with no validation, so a Host: .. header walks one level above the document root. Subsequent file resolution then exposes everything in that parent directory — arbitrary file read, full directory listing, and, if any .lua file is present, server-side Lua execution. This vulnerability is fixed in 1.17.8.
A path traversal vulnerability has been identified in Algernon web server versions prior to 1.17.8. When the server is started with the --domain option (or --letsencrypt, which automatically enables --domain), the request handler resolves the directory to be served by combining the specified --dir option with the client-supplied Host header. This combination is done using filepath.Join without any validation, allowing a Host header value of .. to traverse up one directory level. As a result, files in the parent directory can be accessed, leading to arbitrary file reads, full directory listings, and execution of server-side Lua scripts if a .lua file is present. The vulnerability is particularly concerning in multi-domain HTTPS deployments using Let's Encrypt, where it can be exploited without the server operator's knowledge.
Users can update to Algernon version 1.17.8 or later, where this vulnerability has been fixed.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed May 26, 2026CISA-ADP
Assessed May 26, 2026References to Advisories, Solutions, and Tools
By selecting these links, you will be leaving this site. These are references gathered from the official CVE record and are not endorsed by Volerion.
| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/xyproto/algernon/security/advisories/GHSA-jc3j-x6pg-4hmv | CISA-ADP | AdvisoryExploitRemedyVendor |
| https://github.com/xyproto/algernon/security/advisories/GHSA-jc3j-x6pg-4hmv | [email protected] | AdvisoryExploitRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-22 | Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') | [email protected] |
| CWE-23 | Relative Path Traversal | [email protected] |
| CWE-644 | Improper Neutralization of HTTP Headers for Scripting Syntax | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| Algernon | <= 1.17.7 (semver) |
CPE
Remediation
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Change History
5 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 24, 2026 | CVE Translated | [email protected] |
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| May 26, 2026 | CVE Modified | CISA-ADP |
| May 26, 2026 | New CVE Received | [email protected] |