What is CVE-2026-27613?

CVE-2026-27613 is a critical-severity vulnerability in Maximmasiutin Tinyweb, classified under OS Command Injection. CVSS score: 9.8/10. Published 2026-02-25.

How severe is CVE-2026-27613?

Critical severity. CVSS v3 base score is 9.8 out of 10.

RCE in Maximmasiutin Tinyweb

CVE-2026-27613

TinyWeb is a web server (HTTP, HTTPS) written in Delphi for Win32. A vulnerability in versions prior to 2.01 allows unauthenticated remote attackers to bypass the web server's CGI parameter security controls. Depending on the server configuration and the specific CGI executable in use, the impact is either source code disclosure or remote code execution (RCE). Anyone hosting CGI scripts (particularly interpreted languages like PHP) using vulnerable versions of TinyWeb is impacted. The problem has been patched in version 2.01. If upgrading is not immediately possible, ensure `STRICT_CGI_PARAMS` is enabled (it is defined by default in `define.inc`) and/or do not use CGI executables that natively accept dangerous command-line flags (such as `php-cgi.exe`). If hosting PHP, consider placing the server behind a Web Application Firewall (WAF) that explicitly blocks URL query string parameters that begin with a hyphen (`-`) or contain encoded double quotes (`%22`).

Vulnerability class: Command Injection (OS Command Injection)

Published 2026-02-25 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.015 (74.6th percentile), scored 2026-10-24.

Low probability of exploitation in the next 30 days, but still tracked. 75th percentile — 74.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.014 · newest: 0.015 · change: +0.002

Affected products

Maximmasiutin Tinyweb — versions < 2.01
Ritlabs Tinyweb

Weakness classification (CWE)

References

github.com/maximmasiutin/TinyWeb/security/advisories/GHSA-rfx5-fh9m-9jj9 (Vendor Advisory)
github.com/maximmasiutin/TinyWeb/commit/d9dbda8db49da69d2160e1c527e782b73b5ffb6b (Patch)
github.com/maximmasiutin/TinyWeb/releases/tag/v2.01 (Release Notes)
www.masiutin.net/tinyweb-cve-2026-27613.html (Third Party Advisory)

Frequently asked questions

What is CVE-2026-27613?: CVE-2026-27613 is a critical-severity vulnerability in Maximmasiutin Tinyweb, classified under OS Command Injection. CVSS score: 9.8/10. Published 2026-02-25.
How severe is CVE-2026-27613?: Critical severity. CVSS v3 base score is 9.8 out of 10.