CVE-2026-62389: Allocation of Resources Without Limits or Throttling in websockets ws
ws before 8.21.1 contains a memory exhaustion vulnerability in lib/receiver.js where the fragment guard only triggers when fragment count reaches maxFragments, allowing attackers to exhaust memory by sending incomplete fragmented WebSocket messages. Attackers can send a text frame with FIN=0 followed by continuation frames without completing the sequence, causing each fragment to be stored as a separate Buffer object with significant overhead, enabling denial of service through heap exhaustion.
AI Analysis
Technical Summary
CVE-2026-62389 is a high-severity vulnerability affecting the ws WebSocket library versions prior to 8.21.1. The issue resides in lib/receiver.js where the fragment guard mechanism only activates when the fragment count reaches the configured maxFragments threshold. Attackers can exploit this by sending a text frame with the FIN bit set to 0 followed by multiple continuation frames without completing the sequence. Each fragment is stored as a separate Buffer object, causing significant memory overhead and enabling denial of service via heap exhaustion.
Potential Impact
Successful exploitation allows remote attackers to exhaust server memory by sending incomplete fragmented WebSocket messages, resulting in denial of service conditions. There is no indication of privilege escalation, code execution, or data disclosure from the provided information.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, consider implementing application-level limits on WebSocket message fragmentation or connection timeouts to mitigate potential memory exhaustion.
CVE-2026-62389: Allocation of Resources Without Limits or Throttling in websockets ws
Description
ws before 8.21.1 contains a memory exhaustion vulnerability in lib/receiver.js where the fragment guard only triggers when fragment count reaches maxFragments, allowing attackers to exhaust memory by sending incomplete fragmented WebSocket messages. Attackers can send a text frame with FIN=0 followed by continuation frames without completing the sequence, causing each fragment to be stored as a separate Buffer object with significant overhead, enabling denial of service through heap exhaustion.
CVSS v4.0
Score 8.7high
Affected software
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-62389 is a high-severity vulnerability affecting the ws WebSocket library versions prior to 8.21.1. The issue resides in lib/receiver.js where the fragment guard mechanism only activates when the fragment count reaches the configured maxFragments threshold. Attackers can exploit this by sending a text frame with the FIN bit set to 0 followed by multiple continuation frames without completing the sequence. Each fragment is stored as a separate Buffer object, causing significant memory overhead and enabling denial of service via heap exhaustion.
Potential Impact
Successful exploitation allows remote attackers to exhaust server memory by sending incomplete fragmented WebSocket messages, resulting in denial of service conditions. There is no indication of privilege escalation, code execution, or data disclosure from the provided information.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, consider implementing application-level limits on WebSocket message fragmentation or connection timeouts to mitigate potential memory exhaustion.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-07-13T22:40:54.412Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a57c45668715ace431fc1e7
Added to database: 07/15/2026, 17:33:10 UTC
Last enriched: 07/15/2026, 17:47:26 UTC
Last updated: 07/15/2026, 18:33:10 UTC
Views: 5
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