CVE-2026-0969
📋 TL;DR
CVE-2026-0969 allows remote attackers to execute arbitrary code on servers using next-mdx-remote when processing untrusted MDX content. This occurs because the serialize function doesn't properly sanitize MDX input before server-side rendering. Any application using next-mdx-remote with user-supplied content is affected.
💻 Affected Systems
- next-mdx-remote
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Complete server compromise allowing data theft, lateral movement, and persistent backdoor installation
Likely Case
Server takeover leading to data exfiltration, cryptocurrency mining, or website defacement
If Mitigated
No impact if only trusted MDX content is processed or proper input validation is implemented
🎯 Exploit Status
Exploitation requires ability to submit MDX content for server-side rendering
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check vendor advisory for specific version
Vendor Advisory: https://discuss.hashicorp.com/t/hcsec-2026-01-arbitrary-code-execution-in-react-server-side-rendering-of-untrusted-mdx-content/77155
Restart Required: Yes
Instructions:
1. Review vendor advisory
2. Update next-mdx-remote to patched version
3. Restart application server
4. Test with known safe MDX content
🔧 Temporary Workarounds
Disable untrusted MDX processing
allTemporarily disable server-side rendering of user-supplied MDX content
Modify application code to reject or sanitize all user MDX input
Implement input validation
allAdd strict validation to reject suspicious MDX patterns
Implement regex-based filtering for dangerous MDX constructs
🧯 If You Can't Patch
- Implement strict WAF rules to block suspicious MDX patterns
- Isolate the vulnerable service in a restricted network segment
🔍 How to Verify
Check if Vulnerable:
Check package.json for next-mdx-remote version and review if untrusted MDX is processedCheck Version:
npm list next-mdx-remoteVerify Fix Applied:
Verify updated package version and test with safe MDX content📡 Detection & Monitoring
Log Indicators:
- Unusual process spawns from Node.js
- Suspicious MDX content in request logs
- Error logs from serialize function
Network Indicators:
- Unexpected outbound connections from application server
- Command and control traffic patterns
SIEM Query:
source="application.log" AND "serialize" AND ("error" OR "exception")