CVE-2026-62389
ws < 8.21.1 Default maxFragments Allows Memory Exhaustion DoS
CVSS Score
7.5
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-770 |
| Vendor | websockets |
| Product | ws |
| Published | Jul 15, 2026 |
| Last Updated | Jul 15, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Affected Versions
websockets / ws
0 < 8.21.1
References
github.com: https://github.com/websockets/ws/issues/2331 github.com: https://github.com/websockets/ws/releases/tag/8.21.1 github.com: https://github.com/websockets/ws/commit/f197ac65140920bdcecdab74bfc69c2d7858e55d vulncheck.com: https://www.vulncheck.com/advisories/ws-default-maxfragments-allows-memory-exhaustion-dos
Credits
George Chen