Code Injection in yeswiki/yeswiki (CVE-2026-52778)
Summary
Code injection in yeswiki/yeswiki (CVE-2026-52778). Successful exploitation can lead to full system takeover. Mitigation: upgrade to 4.6.6 or later.
Original description
The description as published by the source.
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:
$regexpToCheckIfMathFormula = '/^((' . $number . '|' . $functions . '\s*\((?1)+\)|\((?1)+\))(?:' . $operators . '(?1))?)+$/';
if (preg_match($regexpToCheckIfMathFormula, $formula)) {
$formula = preg_replace('!pi|π!', 'pi()', $formula);
try {
eval("\$value = $formula;"); // VULNERABLE LINE
// ...
Architectural Flaws
PCRE Stack Overflow & ReDoS (The Immediate Exploit):
The regex definition heavily relies on a recursive pattern (?1)+. In PHP's PCRE engine, deeply nested recursive patterns are processed on the system stack. If an attacker inputs a formula with thou…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-52778 has been found in yeswiki/yeswiki.
Successful exploitation can lead to full system takeover. CVSS score: 9.8/10.
What to do: upgrade yeswiki/yeswiki to 4.6.6 or later.
If unsure, ask your IT team or search "yeswiki/yeswiki CVE-2026-52778" on the vendor's site.
CVE-2026-52778 (yeswiki/yeswiki) — CWE-94 / CVSS v3 9.8
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 4.6.6 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Arbitrary code execution (CWE-94) exists in yeswiki/yeswiki.
Check the vendor advisory for the affected versions of yeswiki/yeswiki.
Severity: Critical (CVSS 9.8/10). Successful exploitation can lead to full system takeover.
Update to 4.6.6.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'yeswiki/yeswiki' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'yeswiki/yeswiki' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
yeswiki/yeswikiを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade yeswiki/yeswiki to 4.6.6ステージング環境で 4.6.6 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory nvd.nist.gov
- package github.com
- web security-advisories@github.com
- web security-advisories@github.com
- web github.com
- web github.com