CVE-2026-26028
MediumCVSS 6.1Exploitation Probability (EPSS)
Low risk15th percentile - higher than 15% of all known CVEs
Summary
CryptPad before 2026.2.0 has an HTML sanitizer bypass in Diffmarked.js. The sanitizer only validates the src attribute of <iframe>, <video>, and <audio> elements, leaving other attributes like srcdoc unchecked. An attacker can inject arbitrary HTML, defeating bounce sandboxing.
Risk Assessment
Users may be tricked into interacting with malicious content, leading to data theft or further XSS attacks.
Recommendation
Update CryptPad to version 2026.2.0 or later, which fixes the sanitizer.
Original NVD description (English source)
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.