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CVE-2026-45721

Algernon - Web Server

xyproto CVSS 9 Updated May 29, 2026

Executive Risk Summary

"A critical vulnerability in Algernon web server allows an unauthenticated attacker to execute system commands on the server by exploiting a directory traversal vulnerability. This vulnerability is fixed in version 1.17.7."

Anticipated Attack Path

  1. 1. An attacker writes a malicious handler.lua file in a parent directory of the server root
  2. 2. The attacker sends an HTTP request to a directory without an index file, triggering the directory traversal vulnerability
  3. 3. The Algernon web server executes the malicious handler.lua file, allowing the attacker to execute system commands

Am I Vulnerable?

  • Check if the Algernon web server version is prior to 1.17.7
  • Verify if any handler.lua files exist in parent directories of the server root
  • Monitor for suspicious HTTP requests to directories without index files

Operational Audit Arsenal

Target Type binary
Target Asset algernon
Standard Path /usr/local/bin/algernon

Manual Verification Required

This is a non-Windows asset (xyproto). Use the target asset details and official path provided above to verify your current version against the official vendor advisories listed below.

Patch Impact Forecast

Reboot Required Unlikely

Minimal

Internal Work Notes

Apply Algernon web server version 1.17.7 to mitigate a critical remote code execution vulnerability

Technical Intelligence & Operational Utilities • Delivered Weekly

Intelligence Sources

Data compiled from NVD, MSRC, and CISA KEV Catalog. Intelligence synthesized via AI. Scripts provided for diagnostic purposes under MIT License.