CVE-2026-48126

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.

• CWE-22
• CWE-23
• CWE-644

• https://github.com/xyproto/algernon/security/advisories/GHSA-jc3j-x6pg-4hmv
• https://github.com/xyproto/algernon/security/advisories/GHSA-jc3j-x6pg-4hmv

Published

May 26, 2026

Last Modified

Jul 24, 2026

Status

Deferred

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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