CVE-2025-66629

In HedgeDoc prior to version 1.11.0, the GitHub Gist export flow had an OAuth2 state validation flaw. The state parameter was only checked for presence, not validated against the user's session, allowing an attacker to forge a callback URL. A logged-in victim clicking a crafted link could export their private note to an attacker-controlled Gist.

HedgeDoc before version 1.11.0 was vulnerable to a YAML alias bomb in note frontmatter. Unsafe parsing with js-yaml.load expanded YAML anchor aliases, creating huge object structures and excessive CPU consumption. An attack could block the Node.js event loop for about 235 seconds per request, causing denial of service (DoS).

HedgeDoc versions prior to 1.11.0 allowed attackers to bypass rate-limiting on /login and /register routes by spoofing the cf-connecting-ip header. The application trusted this header even when the request did not originate from Cloudflare, enabling login spam or mass account creation.

HedgeDoc before version 1.11.0 was vulnerable to stored HTML Injection due to unsafe handling of the local-part of registered email addresses. An attacker could register a specially crafted email address and inject arbitrary HTML into pages viewed by other users.

HedgeDoc prior to version 1.9.9 allowed the creation of notes with an alias matching the ID of existing notes, effectively hiding the original notes. Users could exploit this vulnerability to manipulate note content and prevent access to original notes.