RCE in Xyproto Algernon
CVE-2026-45728
Algernon is a small self-contained pure-Go web server. Prior to 1.17.7, when Algernon is invoked with a single file path instead of a directory, singleFileMode is set to true and debugMode is forcibly enabled. debugMode activates the PrettyError renderer, which on any Lua or template error response dumps the absolute path of the file that errored, complete byte contents of that file, and exception or parser error text. This response is served with HTTP 200 OK to whoever sent the request that triggered the error. Any client able to reach the server and able to provoke a runtime error in the served script obtains the full server-side source of that script and of any sibling Lua data file consulted during the request. This vulnerability is fixed in 1.17.7.
EPSS: 0.003 (22.5th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
Affected products
- Xyproto Algernon — versions < 1.17.7
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM)
Frequently asked questions
- What is CVE-2026-45728?
- CVE-2026-45728 is a high-severity vulnerability in Xyproto Algernon, classified under Generation of Error Message Containing Sensitive Information. CVSS score: 7.5/10. Published 2026-05-26.
- How severe is CVE-2026-45728?
- High severity. CVSS v3 base score is 7.5 out of 10.