CVE-2026-73255 Mongoose: Path traversal in SSI #include directives enables arbitrary file read
An attacker can read arbitrary files by exploiting path traversal in SSI include directives within Mongoose deployments where SSI is enabled.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-73255?
CVE-2026-73255 is a medium-severity path traversal vulnerability in Cesanta Mongoose, published on 20 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Mongoose is an embedded web server and network library. Prior to 7.22, an attacker who can control an SSI-enabled file can place directory traversal sequences in an #include file or #include virtual directive. The mg_ssi() function in src/ssi.c concatenates the directive argument into a filesystem path without calling mg_path_is_sane(), allowing an MG_ENABLE_SSI deployment with ssi_pattern configured to disclose files readable by the Mongoose process. This issue is fixed in version 7.22.
Weakness: CWE-22
Which versions are affected by CVE-2026-73255?
It affects 1 product.
Products include Cesanta Mongoose.
How do I fix CVE-2026-73255?
Upgrade to a fixed version.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-73255 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-73255 exists.
Other vulnerabilities in Cesanta Mongoose
Sources
Also known as DEBIAN-CVE-2026-73255, GHSA-h7m9-764r-7x4x, JLSEC-2026-1379, UBUNTU-CVE-2026-73255.