CVE-2021-29475
Vulnérabilité critique dans hedgedoc (hedgedoc)
Description
HedgeDoc (formerly known as CodiMD) is an open-source collaborative markdown editor. An attacker is able to receive arbitrary files from the file system when exporting a note to PDF. Since the code injection has to take place as note content, there fore this exploit requires the attackers ability to modify a note. This will affect all instances, which have pdf export enabled. This issue has been fixed by https://github.com/hedgedoc/hedgedoc/commit/c1789474020a6d668d616464cb2da5e90e123f65 and is available in version 1.5.0. Starting the CodiMD/HedgeDoc instance with `CMD_ALLOW_PDF_EXPORT=false` or set `"allowPDFExport": false` in config.json can mitigate this issue for those who cannot upgrade. This exploit works because while PhantomJS doesn't actually render the `file:///` references to the PDF file itself, it still uses them internally, and exfiltration is possible, and easy through JavaScript rendering. The impact is pretty bad, as the attacker is able to read the CodiMD/HedgeDoc `config.json` file as well any other files on the filesystem. Even though the suggested Docker deploy option doesn't have many interesting files itself, the `config.json` still often contains sensitive information, database credentials, and maybe OAuth secrets among other things.
Gravité et risque d'exploitation
CVE-2021-29475 obtient un score CVSS de 10.0/10, soit une gravité critique. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 1.16 %, ce qui la place devant 66.6 % des CVE référencées.
Que faire ?
- Vérifiez si hedgedoc (versions < 1.5.0) est présent sur votre parc.
- Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
- À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
- Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.