HedgeDoc is open source software which lets you create real-time collaborative markdown notes. In HedgeDoc before version 1.7.2, an attacker can inject arbitrary JavaScript into a HedgeDoc note, which is executed when the note is viewed in slide mode. Depending on the configuration of the instance, the attacker may not need authentication to create or edit notes. The problem is patched in HedgeDoc 1.7.2. As a workaround, disallow loading JavaScript from 3rd party sites using the `Content-Security-Policy` header. Note that this will break some embedded content.
Conclusion & alert: CVE-2021-21259 is rated High Exploit Risk (69.4/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.35%).Core evidence: 1 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +1.08% over the last day, indicating growing attacker interest.Mandatory action: Public exploits are available—assess exposure, apply mitigations, and prioritize patching.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
Public exploit references (Exploit-DB) for CVE-2021-21259
Exploit prediction scoring system (EPSS) score for CVE-2021-21259
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).