What is CVE-2026-45721?

CVE-2026-45721 is a critical-severity vulnerability in Xyproto Algernon, classified under Improper Input Validation. CVSS score: 9.0/10. Published 2026-05-26.

How severe is CVE-2026-45721?

Critical severity. CVSS v3 base score is 9.0 out of 10.

Improper input validation in Xyproto Algernon

CVE-2026-45721

Algernon is a small self-contained pure-Go web server. Prior to 1.17.7, when Algernon is asked for any URL path that resolves to a directory without an index file, DirPage walks upward through parent directories — past the configured serve…

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

EPSS: 0.002 (44.9th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.0 (Critical). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H.

Affected products

Xyproto Algernon — versions < 1.17.7

Weakness classification (CWE)

CWE-20 — Improper Input Validation
CWE-426 — Untrusted Search Path
CWE-552 — Files or Directories Accessible to External Parties

References

security-advisories@github.com (x_refsource_CONFIRM)

Frequently asked questions

What is CVE-2026-45721?: CVE-2026-45721 is a critical-severity vulnerability in Xyproto Algernon, classified under Improper Input Validation. CVSS score: 9.0/10. Published 2026-05-26.
How severe is CVE-2026-45721?: Critical severity. CVSS v3 base score is 9.0 out of 10.