CVE-2026-52778: Yeswiki

Critical severity, CVSS 9.8. EPSS: 0.8% chance of exploitation in the next 30 days.

YesWiki is a wiki system written in PHP. Prior to version 4.6.6, an unsafe execution vulnerability exists in the Bazar form field calculator (CalcField.php) of YesWiki. The application attempts to sanitize user-defined mathematical formulas using a complex recursive regular expression before passing them to the PHP eval() function. This implementation is inherently flawed: it is vulnerable to Regular Expression Denial of Service (ReDoS / Stack Overflow) which can crash the server, and it creates a high-risk architecture where any logic bypass directly results in arbitrary PHP code execution. Version 4.6.6 patches the issue.

Affected products

• Yeswiki Yeswiki: before 4.6.6 (fixed in 4.6.6)

Published 2026-06-08. Last modified 2026-10-06.