Vulnerability · Published May 26, 2026 · Assigned by GitHub_M

CVE-2026-46430Algernon: Auto-refresh SSE event server binds to all interfaces by default on Linux/macOS

Medium 4.3

In plain English

A medium-severity security flaw in algernon from xyproto. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 9% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)4.3Medium

Exploit odds (30 days)0.2%top 90.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

Algernon is a small self-contained pure-Go web server. Prior to 1.17.7, the SSE event server bound to 0.0.0.0:5553 on Linux/macOS by default because the platform-dependent host default in engine/flags.go:39-46 set host = "" for non-Windows, and utils.JoinHostPort("", ":5553") resolves to ":5553". This vulnerability is fixed in 1.17.7.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Go	github.com/xyproto/algernon	1.17.7	GHSA-gj84-924c-48fx
Go	github.com/xyproto/algernon	1.17.7	GO-2026-5401

Affected products (as reported)

Vendor	Product	Versions
xyproto	algernon	< 1.17.7

Weakness: CWE-668, CWE-1188 · Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

References

https://github.com/xyproto/algernon/security/advisories/GHSA-gj84-924c-48fx x_refsource_CONFIRM