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How CVE-2025-4727 Works
The vulnerability in Meteor (up to v3.2.1) stems from inefficient regular expression handling in the `Object.assign` function within packages/ddp-server/livedata_server.js. The `forwardedFor` argument is processed using a complex regex pattern, leading to potential ReDoS (Regular Expression Denial of Service) attacks. Attackers can exploit this by sending specially crafted input, causing excessive CPU consumption due to backtracking in regex evaluation. Remote exploitation is possible but requires precise timing and payload construction, making it difficult to execute successfully.
DailyCVE Form
Platform: Meteor
Version: ≤ 3.2.1
Vulnerability: ReDoS
Severity: Medium
Date: 2025-06-23
Prediction: Patch expected by 2025-07-10
What Undercode Say
Analytics:
curl -X GET "http://vulnerable-meteor-instance" -H "X-Forwarded-For: malicious_payload"
// Proof-of-Concept Regex Attack const maliciousInput = "a" + "\."repeat(10000) + "x";
How Exploit
Craft a malicious `X-Forwarded-For` header with an overly complex string to trigger regex backtracking, leading to server CPU exhaustion.
Protection from this CVE
- Upgrade to Meteor v3.2.2
- Implement input sanitization
- Use rate-limiting
Impact
- Denial of Service (CPU exhaustion)
- Reduced server availability
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
