YesWiki has Unsafe eval() in its Formula Calculato, Leading to Remote Code Execution & Denial of Service

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

9.8 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

• CVE-2026-52778: 0.80% estimated exploitation activity in the next 30 days; percentile 56.57 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary 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. Details Affected Component - File: tools/bazar/fields/CalcField.php - Method: formatValuesBeforeSave($entry) - Vulnerable Mechanism: Combination of a complex recursive regex validation followed by eval(). The code attempts to implement a sandbox for mathematical operations by verifying the formula structure before executing it: Architectural Flaws PCRE Stack Overflow & ReDoS (The Immediate Exploit): The regex definition heavily relies on a recursive…

Published by the source

9 Jul 2026, 21:03 UTC

Last modified by the source

9 Jul 2026, 21:03 UTC

Source last checked

26 Oct 2026, 14:50 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-px5m-h76g-p7p8

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# Patch Next advisory brief: CVE-2026-52778

Advisory: YesWiki has Unsafe eval() in its Formula Calculato, Leading to Remote Code Execution & Denial of Service
IDs: CVE-2026-52778, GHSA-px5m-h76g-p7p8
Record: https://patchnext.com/advisories/cve-2026-52778 (revision 1, source checked 26 Oct 2026, 14:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: yeswiki/yeswiki 4.6.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist yeswiki/yeswiki: affected < 4.6.6; fixed in 4.6.6

## Suggested inspection (read-only)
- Packagist yeswiki/yeswiki: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on yeswiki/yeswiki.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-px5m-h76g-p7p8 (GitHub-reviewed advisory GHSA-px5m-h76g-p7p8 lists affected ranges: Packagist yeswiki/yeswiki >=0 <4.6.6)

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