GHSA-mj46-r4gr-5x83
HIGHUnsanitized JavaScript code injection possible in gatsby-plugin-mdx
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
gatsby-plugin-mdx📦gatsby-plugin-mdxReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
Description
Impact
The gatsby-plugin-mdx plugin prior to versions 3.15.2 and 2.14.1 passes input through to the gray-matter npm package, which is vulnerable to JavaScript injection in its default configuration, unless input is sanitized. The vulnerability is present when passing input in both webpack (MDX files in src/pages or MDX file imported as component in frontend / React code) and data mode (querying MDX nodes via GraphQL). Injected JavaScript executes in the context of the build server.
To exploit this vulnerability untrusted/unsanitized input would need to be sourced or added into an MDX file. The following MDX payload demonstrates a vulnerable configuration:
---js
((require("child_process")).execSync("id >> /tmp/rce"))
---
Patches
A patch has been introduced in [email protected] and [email protected] which mitigates the issue by disabling the gray-matter JavaScript Frontmatter engine. The patch introduces a new option, JSFrontmatterEngine which is set to false by default. When setting JSFrontmatterEngine to true, input passed to gatsby-plugin-mdx must be sanitized before processing to avoid a security risk. Warnings are displayed when enabling JSFrontmatterEngine to true or if it appears that the MDX input is attempting to use the Frontmatter engine.
Workarounds
If an older version of gatsby-plugin-mdx must be used, input passed into the plugin should be sanitized ahead of processing.
We encourage projects to upgrade to the latest major release branch for all Gatsby plugins to ensure the latest security updates and bug fixes are received in a timely manner.
Credits
We would like to thank Snyk [snyk.io] for initially bringing the issue to our attention, as well as Feng Xiao and Zhongfu Su, who reported the issue to Snyk.
For more information
Email us at [email protected].
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | gatsby-plugin-mdx | all versions | 2.14.1 |
| 📦npm | gatsby-plugin-mdx | ≥ 3.0.0&&< 3.15.2 | 3.15.2 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for gatsby-plugin-mdx. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update gatsby-plugin-mdx to 2.14.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-mj46-r4gr-5x83 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-mj46-r4gr-5x83 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-mj46-r4gr-5x83. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-mj46-r4gr-5x83 in your dependencies?
O3 detects GHSA-mj46-r4gr-5x83 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.