Vulnerability Description
CryptPad is an end-to-end encrypted collaborative office suite. In versions prior to 2026.2.0, the HTML sanitizer in Diffmarked.js can be bypassed due to incomplete attribute filtering on restricted tags. The sanitizer validates only the src attribute of <iframe>, <video>, and <audio> elements, leaving all other attributes unchecked. As a result, an attacker can inject arbitrary HTML through srcdoc, completely defeating CryptPad's intended bounce sandboxing and enabling link injection or other interactive content within user-controlled documents. The root cause lies in how the sanitizer classifies and enforces tag restrictions: although it defines both forbidden and restricted tag lists, <iframe> is treated as "restricted" rather than "forbidden." Enforcement then inspects only the src attribute, so pairing a benign blob: src with a malicious srcdoc results in unrestricted rendering. This issue has been fixed in version 2026.2.0.
CVSS Score
MEDIUM
Related Weaknesses (CWE)
References
- https://github.com/cryptpad/cryptpad/releases/tag/2026.2.0
- https://github.com/cryptpad/cryptpad/security/advisories/GHSA-g2g4-47gv-p72v
FAQ
What is CVE-2026-26028?
CVE-2026-26028 is a vulnerability with a CVSS score of 6.1 (MEDIUM). CryptPad is an end-to-end encrypted collaborative office suite. In versions prior to 2026.2.0, the HTML sanitizer in Diffmarked.js can be bypassed due to incomplete attribute filtering on restricted t...
How severe is CVE-2026-26028?
CVE-2026-26028 has been rated MEDIUM with a CVSS base score of 6.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-26028?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.