CVE-2026-46430 Algernon: Auto-refresh SSE event server binds to all interfaces by default on Linux/macOS
Algernon web server exposes its SSE event server on all network interfaces by default, allowing unauthorized access to event streams.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-46430?
CVE-2026-46430 is a medium-severity vulnerability in xyproto algernon, published on 26 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
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.
Which versions are affected by CVE-2026-46430?
3 open source packages ship an affected version, including github.com/xyproto/algernon.
| Package | Affected | Fixed in |
|---|---|---|
github.com/xyproto/algernon Go | All versions | 1.17.7 |
github.com/xyproto/algernon Go | All versions | 1.17.7 |
github.com/xyproto/algernon Go | All versions | 1.17.7 |
How do I fix CVE-2026-46430?
Upgrade github.com/xyproto/algernon to 1.17.7 or later.
Is CVE-2026-46430 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-46430 exists.
Sources
Also known as GHSA-gj84-924c-48fx, GO-2026-5401.