CVE-2026-52778
CriticalPublic exploitPrior to version 4.6.6, an unsafe execution vulnerability exists in the Bazar form field calculator (CalcField.php) of YesWiki.
Published Jun 8, 2026 · Updated Oct 8, 2026 · Also known as EUVD-2026-35181, GHSA-px5m-h76g-p7p8
Key Facts
Patch immediately- CVE-2026-52778 is a critical-severity vulnerability (CVSS 9.8 v3.1) affecting yeswiki/yeswiki (composer), yeswiki.
- It is not listed in any known-exploited vulnerabilities catalog. Public exploit code is available.
- EPSS estimates a 0.8% probability of exploitation in the next 30 days.
- Fixed versions are available, including yeswiki 4.6.6, yeswiki/yeswiki 4.6.6.
- Brandefense priority: patch immediately, because public exploit code exists for a high-severity flaw.
CVSS v3.1
9.8
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS (30-day exploit likelihood)
0.8%
Exploited in the wild
No known
Not in a known-exploited catalog
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2026-52778 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
Description
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
3 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| yeswiki/yeswikicomposer | See advisory | 4.6.6 |
| yeswiki | >= < 4.6.6 | 4.6.6 |
Patched Releases
yeswiki
4.6.6
yeswiki/yeswiki
4.6.6
Timeline
Publicly disclosed
Jun 8, 2026
Last updated
Oct 8, 2026
Weakness Type
- CWE-94 Improper Control of Generation of Code ('Code Injection')
- CWE-1333 Inefficient Regular Expression Complexity
References
- advisoryGHSA advisory
- advisoryhttps://github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52778.json
- advisoryhttps://nvd.nist.gov/vuln/detail/CVE-2026-52778
- otherhttps://github.com/YesWiki/yeswiki
- otherhttps://github.com/YesWiki/yeswiki/commit/dd2bd8fb099de0d21504bda8a810693b3fcb8e52
FAQ
Common Questions.
YesWiki is a wiki system written in PHP.
Affected: yeswiki/yeswiki (composer); yeswiki versions >= < 4.6.6. The full list is in the CVE brief.
It is not listed in any known-exploited vulnerabilities catalog.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
Public exploit code is available.
Fixed versions are available, including yeswiki 4.6.6, yeswiki/yeswiki 4.6.6.
Brandefense priority: patch immediately, because public exploit code exists for a high-severity flaw.
Is CVE-2026-52778 Running On Your Attack Surface?
Brandefense maps vulnerabilities like this one to your internet-facing assets and tells you exactly where to patch.
Request A Demo