Description
Algernon is a small self-contained pure-Go web server. Prior to 1.17.9, Algernon on Windows selects a file handler in engine/handlers.go by calling filepath.Ext() without first rejecting NTFS-equivalent names such as x.lua::$DATA, x.lua., and x.lua . An unauthenticated client can append one of these suffixes to a public server-side script using the .lua, .tl, .po2, .amber, or .frm extension. The request path passes through URL2filename in utils/files.go, skips the renderer and execution cases, and reaches FilePage, os.Open, ReadAndLogErrors, and ToClient, while NTFS resolves the alias to the underlying script. The server consequently returns raw script source and can expose database credentials, API keys, and the SetCookieSecret value, which may permit forged session cookies. Linux and macOS hosts are not affected by this issue. This issue is fixed in version 1.17.9.
Published: 2026-08-19
Score: 8.7 High
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-mm6c-5j6x-hq8m Algernon vulnerable to server-side script source disclosure on Windows via NTFS filename
History

Wed, 19 Aug 2026 18:30:00 +0000

Type Values Removed Values Added
First Time appeared Xyproto
Xyproto algernon
Vendors & Products Xyproto
Xyproto algernon

Wed, 19 Aug 2026 15:00:00 +0000

Type Values Removed Values Added
Description Algernon is a small self-contained pure-Go web server. Prior to 1.17.9, Algernon on Windows selects a file handler in engine/handlers.go by calling filepath.Ext() without first rejecting NTFS-equivalent names such as x.lua::$DATA, x.lua., and x.lua . An unauthenticated client can append one of these suffixes to a public server-side script using the .lua, .tl, .po2, .amber, or .frm extension. The request path passes through URL2filename in utils/files.go, skips the renderer and execution cases, and reaches FilePage, os.Open, ReadAndLogErrors, and ToClient, while NTFS resolves the alias to the underlying script. The server consequently returns raw script source and can expose database credentials, API keys, and the SetCookieSecret value, which may permit forged session cookies. Linux and macOS hosts are not affected by this issue. This issue is fixed in version 1.17.9.
Title Algernon: Server-side script source disclosure on Windows via NTFS filename
Weaknesses CWE-69
References
Metrics cvssV4_0

{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N'}


Subscriptions

Xyproto Algernon
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-08-19T15:21:04.152Z

Reserved: 2026-06-08T18:02:19.731Z

Link: CVE-2026-52792

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-19T15:17:09.667

Modified: 2026-08-19T16:17:45.810

Link: CVE-2026-52792

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-19T18:15:03Z

Weaknesses
  • CWE-69

    Improper Handling of Windows ::DATA Alternate Data Stream