PT-2026-43308 · Xyproto · Algernon

Published 2026-05-26 · Updated 2026-05-26 · CVE-2026-48126

NVD

CVSS v3.1

8.2

High

Base vector

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

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.

Fix

Relative Path Traversal

Path traversal

Weakness Enumeration

CWE-644

CWE-23

CWE-22

Related Identifiers

CVE-2026-48126

Affected Products

Algernon

References · 2

• https://nvd.nist.gov/vuln/detail/CVE-2026-48126 · Security Note
• https://github.com/xyproto/algernon/security/advisories/GHSA-jc3j-x6pg-4hmv · Note