CVE-2026-43982 Algernon: Path traversal file write via savein()
An attacker can write files to arbitrary locations outside the web root via the savein() function in Algernon web server.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-43982?
CVE-2026-43982 is a high-severity path traversal vulnerability in xyproto algernon, published on 26 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-22
Which versions are affected by CVE-2026-43982?
How do I fix CVE-2026-43982?
No fix has been published for CVE-2026-43982 yet. Limit exposure of the affected software until one is available.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-43982 being exploited?
There is no known exploitation of CVE-2026-43982 in the wild and no public exploit code.
Sources
Also known as GHSA-2j2c-pv62-mmcp.