What is CVE-2026-46431?

CVE-2026-46431 is a medium-severity vulnerability in Xyproto Algernon, classified under Permissive Cross-domain Policy with Untrusted Domains. CVSS score: 4.3/10. Published 2026-05-26.

How severe is CVE-2026-46431?

Medium severity. CVSS v3 base score is 4.3 out of 10.

Vulnerability in Xyproto Algernon

CVE-2026-46431

Algernon is a small self-contained pure-Go web server. Prior to 1.17.7, the SSE event server's Access-Control-Allow-Origin response header was hardcoded to the wildcard * regardless of the caller's Origin. Because EventSource does not pref…

EPSS: 0.000 (9.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N.

Affected products

Xyproto Algernon — versions < 1.17.7

Weakness classification (CWE)

CWE-942 — Permissive Cross-domain Policy with Untrusted Domains

References

security-advisories@github.com (x_refsource_CONFIRM)

Frequently asked questions

What is CVE-2026-46431?: CVE-2026-46431 is a medium-severity vulnerability in Xyproto Algernon, classified under Permissive Cross-domain Policy with Untrusted Domains. CVSS score: 4.3/10. Published 2026-05-26.
How severe is CVE-2026-46431?: Medium severity. CVSS v3 base score is 4.3 out of 10.