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CVE-2026-52778 Elastic Security · Elastic

Detect YesWiki Formula Calculator Unsafe eval() Remote Code Execution (CVE-2026-52778) in Elastic Security

YesWiki prior to 4.6.6 exposes an unsafe PHP eval() call in its Formula Calculator feature (BazaR calculated field logic). An unauthenticated or low-privileged attacker can craft a malicious formula expression that is passed directly into eval(), resulting in arbitrary PHP code execution on the underlying web server, or a crafted expression that triggers resource exhaustion / infinite loops causing denial of service. Successful exploitation grants the attacker the privileges of the web server process, enabling webshell deployment, credential theft, and lateral movement.

MITRE ATT&CK

Tactic
Initial Access Execution Impact

Elastic Detection Query

Elastic Security (Elastic)
eql 
any where event.dataset == "nginx.access" and
  (url.original : "*BF_formula*" or url.original : "*BazaR*" or url.original : "*formulaire*") and
  (url.original : "*eval(*" or url.original : "*system(*" or url.original : "*exec(*" or url.original : "*base64_decode*" or url.original : "*shell_exec*")
critical severity medium confidence

Identifies HTTP requests to YesWiki formula calculator endpoints carrying suspicious PHP function call strings that indicate exploitation of the unsafe eval() vulnerability.

Data Sources

Nginx Access LogsHTTP Proxy Logs

Required Tables

logs-nginx.access-*

False Positives & Tuning

  • Authorized penetration testing traffic
  • Legitimate wiki content containing formula-related keywords
  • Automated content scrapers indexing wiki pages

Other platforms for CVE-2026-52778

Microsoft Sentinel (KQL) Splunk (SPL) IBM QRadar (QRadar) Sumo Logic CSE (Sumo) Google Chronicle (YARA-L) CrowdStrike LogScale (LogScale) All platforms (combined) →

Testing Methodology

Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.

  1. Test 1Simulate malicious formula eval() payload submission

    Expected signal: Web server access log entry showing POST to /?BazaR/formulaire with body containing 'eval(system(' string; PHP error log may show eval() execution or error

  2. Test 2Simulate DoS payload via infinite loop formula expression

    Expected signal: Elevated CPU utilization on the web server host, PHP-FPM worker timeout/kill logs, web access log entry for the formula endpoint request

  3. Test 3Simulate webshell drop attempt post-exploitation

    Expected signal: File creation event under the YesWiki webroot captured by FIM/EDR, web access log entry for the formula endpoint, PHP-FPM process spawning shell command

Last updated: 2026-07-25 Research depth: standard
References (5)

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