Vulnerability · Published Aug 19, 2026 · Assigned by GitHub_M
CVE-2026-52792Algernon: Server-side script source disclosure on Windows via NTFS filename
High 8.7
In plain English
A high-severity security flaw in algernon from xyproto. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 50% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/xyproto/algernon | 1.17.9 | GO-2026-5903 |
| Go | github.com/xyproto/algernon | 1.17.9 | GHSA-mm6c-5j6x-hq8m |
Affected products (as reported)
Weakness: CWE-69 · 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
References
- https://github.com/xyproto/algernon/security/advisories/GHSA-mm6c-5j6x-hq8m x_refsource_CONFIRM
- https://github.com/xyproto/algernon/commit/a6b0724928a0c35a29640b18ad5bd547f5e2efa6 x_refsource_MISC
- https://github.com/xyproto/algernon/releases/tag/v1.17.9 x_refsource_MISC