HedgeDoc: Denial-of-service via YAML alias expansion in note frontmatter

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Summary

CVECVE-2026-58486
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-13 23:16:47 UTC
Updated2026-07-14 16:42:11 UTC
DescriptionHedgeDoc 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.

Risk And Classification

Primary CVSS: v4.0 8.3 HIGH from [email protected]

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Problem Types: CWE-400 | CWE-409 | CWE-400 CWE-400: Uncontrolled Resource Consumption | CWE-409 CWE-409: Improper Handling of Highly Compressed Data (Data Amplification)

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary8.3HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:X/C...
4.0CNADECLARED8.3HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
Low
User Interaction
None
Confidentiality
None
Integrity
None
Availability
High
Sub Conf.
None
Sub Integrity
None
Sub Availability
High

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Hedgedoc Hedgedoc affected < 1.11.0 Not specified

References

ReferenceSourceLinkTags
github.com/hedgedoc/hedgedoc/security/advisories/GHSA-qj78-mjch-wwrv [email protected] github.com
github.com/hedgedoc/hedgedoc/commit/c489497e451887bfe400434c5a010940051e... [email protected] github.com
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