CVE-2026-58486 HedgeDoc: Denial-of-service via YAML alias expansion in note frontmatter
Attackers can cause denial of service in HedgeDoc by submitting malicious YAML frontmatter that exhausts CPU resources via alias expansion.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-58486?
CVE-2026-58486 is a high-severity denial of service vulnerability in hedgedoc, published on 13 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-58486?
How do I fix CVE-2026-58486?
No fix has been published for CVE-2026-58486 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-58486 being exploited?
There is no known exploitation of CVE-2026-58486 in the wild and no public exploit code.
Sources
Also known as GHSA-qj78-mjch-wwrv.