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.

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact High

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Exploitation none

Automatable yes

Technical Impact partial

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
websockets ws unaffected
Version Status Constraints
0 affected < 8.21.1

No data.

No data.

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Vendors Products
Websockets Subscribe
Ws Subscribe

Project Subscriptions

Vendors Products
Websockets Subscribe
Ws Subscribe
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/websockets/ws/commit/f197ac65140920bdcecdab74bfc69c2d7858e55d cve-icon
https://github.com/websockets/ws/issues/2331 cve-icon
https://github.com/websockets/ws/releases/tag/8.21.1 cve-icon
https://www.vulncheck.com/advisories/ws-default-maxfragments-allows-memory-exhaustion-dos cve-icon
History

Thu, 16 Jul 2026 00:00:00 +0000

Type Values Removed Values Added
First Time appeared Websockets
Websockets ws
Vendors & Products Websockets
Websockets ws

Wed, 15 Jul 2026 18:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Wed, 15 Jul 2026 17:30:00 +0000

Type Values Removed Values Added
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.
Title ws < 8.21.1 Default maxFragments Allows Memory Exhaustion DoS
Weaknesses CWE-770
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_0

{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-07-15T17:55:32.359Z

Reserved: 2026-07-13T22:40:54.412Z

Link: CVE-2026-62389

cve-icon Vulnrichment

Updated: 2026-07-15T17:55:28.387Z

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-07-15T23:45:15Z

Weaknesses