CVE-2021-43838

Name: CVE-2021-43838
Creator: NVD / NIST
Published: 2021-12-17T19:15:07.683+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 1.38%

Last modified Jun 17, 2026

CVE-2021-43838 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. jsx-slack is a library for building JSON objects for Slack Block Kit surfaces from JSX. In versions prior to 4.5.1 users are vulnerable to a regular expression denial-of-service (ReDoS) attack. EPSS estimates a 1.38% chance of exploitation in the next 30 days.

Description

jsx-slack is a library for building JSON objects for Slack Block Kit surfaces from JSX. In versions prior to 4.5.1 users are vulnerable to a regular expression denial-of-service (ReDoS) attack. If attacker can put a lot of JSX elements into `<blockquote>` tag, an internal regular expression for escaping characters may consume an excessive amount of computing resources. jsx-slack v4.5.1 has patched to a regex for escaping blockquote characters. Users are advised to upgrade as soon as possible.

Metrics

CVSS 3.1

7.5/10

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

EPSS Probability

1.38%

68.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Jsx-Slack Project	Jsx-Slack	< 4.5.2

References

https://github.com/yhatt/jsx-slack/commit/36e4a10405e4c7745333e245fcc5029c02c7065dPatch, Third Party Advisory
https://github.com/yhatt/jsx-slack/security/advisories/GHSA-55xv-f85c-248qExploit, Patch, Third Party Advisory
https://github.com/yhatt/jsx-slack/commit/36e4a10405e4c7745333e245fcc5029c02c7065dPatch, Third Party Advisory
https://github.com/yhatt/jsx-slack/security/advisories/GHSA-55xv-f85c-248qExploit, Patch, Third Party Advisory

Timeline

Published: Dec 17, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-43838?

How severe is CVE-2021-43838?

CVE-2021-43838 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 1.38% probability of exploitation in the next 30 days.

How do I fix CVE-2021-43838?

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-2021-43838?

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

Scan your code now

Source: NVD / NIST