dbcve.org
Code InjectionWeakness · CWE-94

CVE-2026-52778

CRITICAL · 9.8 CVSS v3.1 Published 2026-06-08
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

YesWiki versions prior to 4.6.6 contain an unsafe execution vulnerability in the Bazar form field calculator (CalcField.php). The application uses a complex recursive regular expression to sanitize user-defined mathematical formulas before passing them to PHP's eval() function. This approach is fundamentally flawed—it is vulnerable to ReDoS/Stack Overflow attacks that can crash the server, and any bypass of the sanitization logic enables arbitrary PHP code execution.

MitigationUpgrade YesWiki to version 4.6.6 or later to patch the unsafe eval() vulnerability. Until patched, restrict access to Bazar form functionality and monitor for unusual server behavior or ReDoS attack patterns.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Locate the YesWiki installation directory
    Identify the web-accessible directory where YesWiki is installed. Common paths include /var/www/html/, /home/*/public_html/, or check your web server configuration.
    Affected if The installation directory contains YesWiki files.
  2. Identify the installed YesWiki version
    Check for a version indicator in the root directory - look for a version.php, index.php, or a hidden .git directory that may contain version information. Many YesWiki installations include a tools/备/info.json or similar version file.
    Affected if The installed version is prior to 4.6.6 (or cannot be determined to be 4.6.6 or later).
  3. Locate CalcField.php in the installation
    Search for the file CalcField.php within the YesWiki installation. Common paths include tools/bazar/fields/ or tools/ if it exists.
    Affected if CalcField.php exists in the installation.
  4. Verify the vulnerable eval() pattern in CalcField.php
    Open CalcField.php and search for the presence of eval() function calls used to execute mathematical formulas. Look for code that passes user-controlled input to eval() after regex sanitization.
    Affected if CalcField.php contains eval() used to execute sanitized mathematical formulas (indicating the unsafe pattern described).
  5. Determine if Bazar form calculator is accessible
    Check if Bazar form functionality is enabled and accessible on the YesWiki site. This typically involves checking if the Bazar tool is installed and if form fields with calculator capabilities can be created or accessed.
    Affected if Bazar form field calculator functionality is enabled and accessible to users.

If the installed YesWiki version is below 4.6.6, CalcField.php with unsafe eval() exists, and Bazar calculator functionality is accessible, the environment is affected by this vulnerability.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Patch available Apply the vendor patch
Vendor patch github.com →
Interim mitigation

Upgrade YesWiki to version 4.6.6 or later to patch the unsafe eval() vulnerability. Until patched, restrict access to Bazar form functionality and monitor for unusual server behavior or ReDoS attack patterns.

Recommended fix High confidence

YesWiki version 4.6.6

  1. 1. Back up your current YesWiki installation including all files, database, and configuration.
  2. 2. Check your current YesWiki version (typically in the wiki or a version file).
  3. 3. If running a version prior to 4.6.6, download YesWiki version 4.6.6 from the official repository or release channel.
  4. 4. Replace the existing YesWiki files with the new version 4.6.6 files, preserving your configuration and data files.
  5. 5. Clear any caches if your installation uses caching.
  6. 6. Verify the upgrade by checking that CalcField.php has been updated and the vulnerable code is removed.
  7. 7. Test that Bazar form field calculator functionality works correctly with the patch applied.

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
Get the patch applied

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,408.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-52778 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data