CVE-2021-32723: Regular Expression Denial of Service (ReDoS) in PrismJS
Summary
CVE-2021-32723: Regular Expression Denial of Service (ReDoS) in Prism. Affects prismjs versions < 1.24.0. Fixed in 1.24.0. How to fix ↓
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Background
PrismJS is an open-source syntax highlighting library used to add color and formatting to code snippets on websites. It supports various programming languages and markup formats. However, versions before 1.24.0 are susceptible to a Regular Expression Denial of Service (ReDoS) vulnerability.
Vulnerability Detail
The vulnerability arises when Prism is employed to highlight untrusted text provided by users. An attacker can create a specially crafted string that will cause the highlighting process to take an extremely long time, potentially leading to a denial of service. This vulnerability affects the ASCIIDoc and ERB languages, while other languages remain unaffected.
How To Fix
Latest published version: 1.30.0 as of 23 Oct 2026
npm install prismjs@1.30.0Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
1.24.0
This is the first release that contains the fix.
npm install prismjs@1.24.0Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
There is no known workaround for this vulnerability. Updating to the fixed version is the recommended solution.
Conclusion
The Regular Expression Denial of Service vulnerability in PrismJS versions prior to 1.24.0 can be mitigated by updating to the fixed version. It is recommended to promptly update the library to ensure the security and stability of code highlighting functionality. For further assistance or support in addressing this vulnerability, please contact DevNack.com.
See every vulnerability recorded for prismjs →
FAQ
Versions prior to 1.24.0 are vulnerable to this Regular Expression Denial of Service (ReDoS) issue.
An attacker can exploit this vulnerability to cause a denial of service by providing a specially crafted string that takes an excessively long time to highlight.
The ASCIIDoc and ERB languages are affected. Other languages supported by PrismJS are not vulnerable.
No, there is no known workaround. Updating to the fixed version is the recommended solution.
You can find more information in the GitHub advisory for this vulnerability: https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2021/06/GHSA-gj77-59wh-66hg/GHSA-gj77-59wh-66hg.json
References
Related vulnerabilities
Recent vulnerabilities recorded for prismjs.
