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TI-2021-19644 Aliases CVE-2021-43838GHSA-55xv-f85c-248q

Regular Expression Denial of Service (ReDoS) in jsx-slack

Priority LOW 36CWE-400Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and GitHub. Impact type from CWE-400.

Summary

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.

Why it matters now

EPSS 0.01422 73rd percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed jsx-slack (yhatt): 4.5.1jsx-slack (npm): 4.5.1

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
yhattjsx-slackbefore 4.5.14.5.1Patch availableCNA
—jsx-slack (npm)before 4.5.14.5.1Patch availableGHSA-55xv-f85c-248q
  • jsx-slack Vendoryhatt Affected before 4.5.1 Fixed in 4.5.1 Patch available CNA
  • jsx-slack (npm) Vendor— Affected before 4.5.1 Fixed in 4.5.1 Patch available GHSA-55xv-f85c-248q

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:jsx-slack_project:jsx-slack:*:*:*:*:*:node.js:*:*before 4.5.2VulnerableJsx-slack Project
  • cpe:2.3:a:jsx-slack_project:jsx-slack:*:*:*:*:*:node.js:*:* Versions before 4.5.2 Vulnerable ·Jsx-slack Project

Remediation

  • Fix · CNA jsx-slack (yhatt) Fixed in 4.5.1
  • Fix · GHSA-55xv-f85c-248q jsx-slack (npm) Fixed in 4.5.1 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-43838
  2. 2026-10-03 Alias added: GHSA-55xv-f85c-248q

References

Exploit 1

Patch 1

Advisory 1

Other 1

  • TI-2021-19649 Insufficient patch for Regular Expression Denial of Service (ReDoS) to jsx-slack v4.5.1 CVSS 3.1HIGH 7.5

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences