CVE-2021-4236
CVSS v3
9.8
CRITICAL
EPSS Score
1.1 %
exploit probability, as of 2026-09-25
CISA KEV
No
known exploited
Exploitation
—
SSVC status
Description
Web Sockets do not execute any AuthenticateMethod methods which may be set, leading to a nil pointer dereference if the returned UserData pointer is assumed to be non-nil, or authentication bypass. This issue only affects WebSockets with an AuthenticateMethod hook. Request handlers that do not explicitly use WebSockets are not vulnerable.
Technical details
- Published
- 2022-12-27
Frequently asked questions
What is CVE-2021-4236?
Web Sockets do not execute any AuthenticateMethod methods which may be set, leading to a nil pointer dereference if the returned UserData pointer is assumed to be non-nil, or authentication bypass. This issue only affects WebSockets with an AuthenticateMethod hook. Request handlers that do not explicitly use WebSockets are not vulnerable.
Is CVE-2021-4236 actively exploited?
Active exploitation of CVE-2021-4236 has not been confirmed. Its EPSS score was 1.1% on 2026-09-25, the estimated probability of exploitation in the next 30 days.
What is the CVSS score for CVE-2021-4236?
CVE-2021-4236 has a CVSS v3 base score of 9.8 (CRITICAL severity).
Is CVE-2021-4236 affecting your environment?
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