Summary
Regex denial of service vulnerability in codesample plugin
Workarounds
To work around this vulnerability, either:
- Upgrade to TinyMCE 5.6.0 or higher
- Disable the
codesampleplugin - Disable ruby code samples using the codesample_languages setting
- Override the PrismJS syntax highlighter to version 1.21.0 or higher using the codesample_global_prismjs setting
Acknowledgements
Tiny Technologies would like to thank Erik Krogh Kristensen at GitHub for discovering this vulnerability.
References
https://www.tiny.cloud/docs/release-notes/release-notes56/#securityfixes
For more information
If you have any questions or comments about this advisory:
- Open an issue in the TinyMCE repo
- Email us at [email protected]
Impact
A regex denial of service (ReDoS) vulnerability was discovered in a dependency of the codesample plugin. The vulnerability allowed poorly formed ruby code samples to lock up the browser while performing syntax highlighting. This impacts users of the codesample plugin using TinyMCE 5.5.1 or lower.
Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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This vulnerability has been patched in TinyMCE 5.6.0 by upgrading to a version of the dependency without the vulnerability.
Frequently Asked Questions
- What is GHSA-H96F-FC7C-9R55? GHSA-H96F-FC7C-9R55 is a low-severity uncontrolled resource consumption vulnerability in tinymce (npm), affecting versions < 5.6.0. It is fixed in 5.6.0. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
- Which versions of tinymce are affected by GHSA-H96F-FC7C-9R55? tinymce (npm) versions < 5.6.0 is affected.
- Is there a fix for GHSA-H96F-FC7C-9R55? Yes. GHSA-H96F-FC7C-9R55 is fixed in 5.6.0. Upgrade to this version or later.
- Is GHSA-H96F-FC7C-9R55 exploitable, and should I be worried? Whether GHSA-H96F-FC7C-9R55 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-H96F-FC7C-9R55 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix GHSA-H96F-FC7C-9R55? Upgrade
tinymceto 5.6.0 or later.