xyproto algernon up to 1.17.5 lua/upload/upload.go uploadedFileSaveIn path traversal

Summaryinfo

A vulnerability labeled as critical has been found in xyproto algernon up to 1.17.5. This impacts the function uploadedFileSaveIn of the file lua/upload/upload.go. Executing a manipulation can lead to path traversal. The identification of this vulnerability is CVE-2026-43982. The attack may be launched remotely. There is no exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in xyproto algernon up to 1.17.5. It has been declared as critical. This vulnerability affects the function uploadedFileSaveIn of the file lua/upload/upload.go. The manipulation with an unknown input leads to a path traversal vulnerability. The CWE definition for the vulnerability is CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. As an impact it is known to affect integrity, and availability. CVE summarizes:

Algernon is a small self-contained pure-Go web server. Prior to 1.17.6, uploadedFileSaveIn() in lua/upload/upload.go uses filepath.Join() with the caller-supplied directory but performs no boundary check after joining. A directory of ../../../tmp resolves cleanly to /tmp, outside the web root. This vulnerability is fixed in 1.17.6.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-43982 since 05/04/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1006.

Upgrading to version 1.17.6 eliminates this vulnerability.

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Productinfo

Vendor

• xyproto

Name

• algernon

Version

• 1.17.0
• 1.17.1
• 1.17.2
• 1.17.3
• 1.17.4
• 1.17.5

Website

• Product: https://github.com/xyproto/algernon/

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