Algernon: Auto-refresh SSE event server binds to all interfaces by default on Linux/macOS
Priority MEDIUM 53CWE-1188Published · Updated
Key facts
- Attack vector
- Adjacent network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Information disclosure
- Confidentiality · integrity · availability
- Low · None · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-668 and the CVSS impact.
Summary
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.
Why it matters now
Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00197 9th percentileScored 2026-11-07
Fix Fixed algernon (xyproto): 1.17.7github.com/xyproto/algernon (Go): 1.17.7
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| xyproto | algernon | before 1.17.7 | 1.17.7 | Patch available | CNA |
| — | github.com/xyproto/algernon (Go) | before 1.17.7 | 1.17.7 | Patch available | GHSA-gj84-924c-48fx |
- algernon Vendorxyproto Affected before 1.17.7 Fixed in 1.17.7 Patch available CNA
- github.com/xyproto/algernon (Go) Vendor— Affected before 1.17.7 Fixed in 1.17.7 Patch available GHSA-gj84-924c-48fx
Remediation
- Fix · CNA algernon (xyproto) Fixed in 1.17.7
- Fix · GHSA-gj84-924c-48fx github.com/xyproto/algernon (Go) Fixed in 1.17.7 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-46430
- 2026-10-03 Alias added: GHSA-gj84-924c-48fx
References
More xyproto vulnerabilities
- TI-2026-37902 Algernon: Server-side script source disclosure on Windows via NTFS filename CVSS 4.0HIGH 8.7
- TI-2026-35564 Algernon: Host header path traversal in --domain mode reads files and runs Lua from parent dir CVSS 3.1HIGH 8.2
- TI-2026-33460 Algernon: handler.lua discovery walks parent directories above the server root CVSS 3.1CRITICAL 9.0
- TI-2026-33466 Algernon: Single-file mode unconditionally enables debug mode CVSS 3.1HIGH 7.5
- TI-2026-34142 Algernon: Auto-refresh SSE event server sets Access-Control-Allow-Origin: * CVSS 3.1MEDIUM 4.3
- TI-2026-32026 Algernon: Path traversal file write via savein() CVSS 4.0HIGH 8.7
Sources
- CVE-2026-46430 · CVE Program
- CVE-2026-46430 · NVD
- FIRST EPSS
- GHSA-gj84-924c-48fx · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences