CVE-2026-52792

Algernon: Server-side script source disclosure on Windows via NTFS filename

HIGH

8.7

CVSS Score

Published: August 19, 2026 at 02:49 PM UTC

Updated: September 18, 2026 at 08:19 PM UTC

1 product affected across 1 vendorAlgernon

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Severity

HIGH8.7

Exploit prediction

EPSS 0.6%

SSVC

PoC

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.