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TI-2026-33466 Aliases CVE-2026-45728GHSA-fwqx-8365-9983

Algernon: Single-file mode unconditionally enables debug mode

Priority HIGH 72CWE-1188Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Information disclosure
Confidentiality · integrity · availability
High · None · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-209.

Summary

Algernon is a small self-contained pure-Go web server. Prior to 1.17.7, when Algernon is invoked with a single file path instead of a directory, singleFileMode is set to true and debugMode is forcibly enabled. debugMode activates the PrettyError renderer, which on any Lua or template error response dumps the absolute path of the file that errored, complete byte contents of that file, and exception or parser error text. This response is served with HTTP 200 OK to whoever sent the request that triggered the error. Any client able to reach the server and able to provoke a runtime error in the served script obtains the full server-side source of that script and of any sibling Lua data file consulted during the request. This vulnerability is fixed in 1.17.7.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00303 23rd 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
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
xyprotoalgernonbefore 1.17.71.17.7Patch availableCNA
—github.com/xyproto/algernon (Go)before 1.17.71.17.7Patch availableGHSA-fwqx-8365-9983
  • 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-fwqx-8365-9983

Remediation

  • Fix · CNA algernon (xyproto) Fixed in 1.17.7
  • Fix · GHSA-fwqx-8365-9983 github.com/xyproto/algernon (Go) Fixed in 1.17.7 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-45728
  2. 2026-10-03 Alias added: GHSA-fwqx-8365-9983

References

Other 2

  • 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-2026-34142 Algernon: Auto-refresh SSE event server sets Access-Control-Allow-Origin: * CVSS 3.1MEDIUM 4.3
  • TI-2026-34141 Algernon: Auto-refresh SSE event server binds to all interfaces by default on Linux/macOS CVSS 3.1MEDIUM 4.3
  • TI-2026-32026 Algernon: Path traversal file write via savein() CVSS 4.0HIGH 8.7
See all 7 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences