CVE-2021-4236

Name: CVE-2021-4236
Creator: NVD / NIST
Published: 2022-12-27T22:15:12.013+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 1.12%

Last modified Jun 17, 2026

CVE-2021-4236 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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. EPSS estimates a 1.12% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

1.12%

61.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-476

Affected Software

Vendor	Product	Versions
Web Project	Web	>= 1.4.0, < 1.5.2

References

https://github.com/ecnepsnai/web/commit/5a78f8d5c41ce60dcf9f61aaf47a7a8dc3e0002fPatch, Third Party Advisory
https://pkg.go.dev/vuln/GO-2021-0107Exploit, Patch, Third Party Advisory
https://github.com/ecnepsnai/web/commit/5a78f8d5c41ce60dcf9f61aaf47a7a8dc3e0002fPatch, Third Party Advisory
https://pkg.go.dev/vuln/GO-2021-0107Exploit, Patch, Third Party Advisory

Timeline

Published: Dec 27, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-4236?

How severe is CVE-2021-4236?

CVE-2021-4236 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 1.12% probability of exploitation in the next 30 days.

How do I fix CVE-2021-4236?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-4236?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST