CVE-2026-27613
CGI Parameter Bypass in TinyWeb Allows RCE and Disclosure
Publication date: 2026-02-25
Last updated on: 2026-03-04
Assigner: GitHub, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| ritlabs | tinyweb | to 2.01 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-88 | The product constructs a string for a command to be executed by a separate component in another control sphere, but it does not properly delimit the intended arguments, options, or switches within that command string. |
| CWE-78 | The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability affects TinyWeb, a web server written in Delphi for Win32, in versions prior to 2.01. It 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, this can lead to either source code disclosure or remote code execution (RCE).
The vulnerability is particularly impactful for anyone hosting CGI scripts, especially those using interpreted languages like PHP.
The issue has been patched in version 2.01. If upgrading is not immediately possible, mitigations include enabling STRICT_CGI_PARAMS and avoiding CGI executables that accept dangerous command-line flags, such as php-cgi.exe. Additionally, placing the server behind a Web Application Firewall (WAF) that blocks certain URL query string parameters can help.
How can this vulnerability impact me? :
The vulnerability can have severe impacts depending on the server setup.
- Source code disclosure: Attackers may gain access to the source code of CGI scripts, potentially exposing sensitive information.
- Remote code execution (RCE): Attackers may execute arbitrary code on the server remotely without authentication.
These impacts can compromise the security and integrity of the server and any data it handles.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability immediately, upgrade TinyWeb to version 2.01 or later where the issue is patched.
If upgrading is not possible right away, ensure that the STRICT_CGI_PARAMS setting is enabled (it is defined by default in define.inc).
Avoid using CGI executables that accept dangerous command-line flags, such as php-cgi.exe.
If hosting PHP, consider placing the server behind a Web Application Firewall (WAF) that blocks URL query string parameters beginning with a hyphen (-) or containing encoded double quotes (%22).