Detects RCE indicators related to the proof-of-concept code for the React Server Remote Code Execution Vulnerability (CV

Hunt Hypothesis

This hunt hypothesis identifies adversaries exploiting the React Server Remote Code Execution vulnerability (CVE-2025-55182) to execute arbitrary commands and gain initial access within web application environments. Proactive hunting for these specific RCE indicators in Azure Sentinel is critical to detect early-stage exploitation attempts before attackers can establish persistence or escalate privileges.

YARA Rule

rule EXPL_RCE_React_Server_CVE_2025_55182_POC_Dec25 {
   meta:
      description = "Detects RCE indicators related to the proof-of-concept code for the React Server Remote Code Execution Vulnerability (CVE-2025-55182)"
      author = "Florian Roth"
      reference = "https://www.youtube.com/watch?v=MmdwakT-Ve8"
      date = "2025-12-05"
      score = 70
      id = "fdd661a9-0532-5246-b744-0c1a9632d1cd"
   strings:
      $s1 = "process.mainModule.require('child_process').execSync("
      $s2 = "$1:constructor:constructor"
   condition:
      all of them
      // not XML
      and not uint16(0) == 0x3c3f
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 2 string patterns in its detection logic.

References

• https://www.youtube.com/watch?v=MmdwakT-Ve8
• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios and corresponding exclusion strategies for the React Server RCE Vulnerability (CVE-2025-55182) detection rule:

• Scheduled Deployment Pipelines in CI/CD Environments

  • Scenario: Automated build agents (e.g., GitHub Actions, GitLab Runners, or Jenkins) executing the React Server proof-of-concept code to validate new versions during nightly builds. These jobs often instantiate temporary containers that trigger RCE indicators as they process test payloads against the vulnerable server endpoint.
  • Filter/Exclusion: Create a rule exclusion based on the Source Hostname or Process Name. Exclude any events originating from known CI/CD runner hostnames (e.g., ci-runner-prod-01, jenkins-agent-node) or processes named docker-containerd and kubectl when running within the deployment-pipeline namespace.

• Automated Security Scanning and Vulnerability Assessment

  • Scenario: Internal security tools like Tenable Nessus, Qualys, or Nmap performing active vulnerability scans against the React Server infrastructure. These scanners often send proof-of-concept (PoC) payloads to verify the presence of CVE-2025-55182, which naturally triggers the RCE detection logic as “suspicious activity.”
  • Filter/Exclusion: Implement a time-based exclusion window or source IP filtering. Exclude alerts generated by the dedicated scanning subnet (e.g., 10.20.30.0/24) or specific scanner IPs during scheduled maintenance windows (e.g., Sundays between 02:00 and 06:00 UTC).

• Internal Developer Sandbox Testing

  • Scenario: Developers in the R&D department running local instances