CVE-2026-58486
HighCVSS 8.3Exploitation Probability (EPSS)
Low risk14th percentile - higher than 14% of all known CVEs
Summary
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).
Risk Assessment
The risk is a complete blockage of the HedgeDoc instance by a single malicious payload, making notes inaccessible and causing requests to hang or drop. The attack persists in the database and survives process restarts until the note is removed.
Recommendation
Immediately upgrade HedgeDoc to version 1.11.0 or later, which includes the fix. If upgrading is not possible, temporarily disable the publish view (/s/<shortid>) and editor view (/<noteId>) or restrict access to the instance.
Other vulnerabilities in HedgeDoc
See all- CVE-2026-58489Medium
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.
- CVE-2026-58488Medium
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.
- CVE-2026-58487Medium
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.
- CVE-2023-38487Medium
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.
Original NVD description (English source)
HedgeDoc is an open source, real-time, collaborative, markdown notes application. Prior to version 1.11.0, HedgeDoc was vulnerable to a YAML alias bomb due to unsafe processing of the note frontmatter. HedgeDoc parsed frontmatter with js-yaml.load (js-yaml v3) via @hedgedoc/meta-marked, which resolved YAML anchor aliases. A compact malicious payload could therefore expand into a huge object structure, consuming excessive CPU. This expansion ran on every request to the publish view (/s/<shortid>) and, when placed under the opengraph key, the editor view (/<noteId>). A ten-level alias bomb could block the single Node.js event loop for roughly 235 seconds per request, causing concurrent requests to hang or drop and rendering the instance unavailable (DoS). Because the note was stored in the database, the impact survived process restarts until the note was removed. toobusy-js did not reliably mitigate the worst cases, as the event loop was saturated before the middleware could respond. This issue was fixed in version 1.11.0.