CVE-2026-43982: Xyproto Algernon

High severity, CVSS 8.7. EPSS: 0.5% chance of exploitation in the next 30 days.

Algernon is a small self-contained pure-Go web server. Prior to 1.17.6, uploadedFileSaveIn() in lua/upload/upload.go uses filepath.Join() with the caller-supplied directory but performs no boundary check after joining. A directory of ../../../tmp resolves cleanly to /tmp, outside the web root. This vulnerability is fixed in 1.17.6.

Affected products

• Xyproto Algernon: before 1.17.6 (fixed in 1.17.6)

Published 2026-05-26. Last modified 2026-07-24.