CVE-2022-24837 is a medium-severity vulnerability affecting HedgeDoc, an open-source, web-based, self-hosted collaborative markdown editor widely used for note-taking and document collaboration. The vulnerability exists in HedgeDoc versions 1.9.1 and 1.9.2, where images uploaded to the platform receive filenames that are enumerable and predictable. This predictable filename generation allows unauthorized actors to enumerate and access uploaded images, potentially exposing sensitive information contained within private notes or documents. The issue affects all upload backends except Lutim and Imgur, meaning that if a deployment uses the default or other supported backends, the risk of information leakage is present. The vulnerability is classified under CWE-200, indicating exposure of sensitive information to unauthorized actors. The root cause is the use of a non-random, sequential or guessable filename generation scheme for uploaded images, which makes it feasible for attackers to guess URLs of uploaded files. This issue was addressed in HedgeDoc version 1.9.3 by replacing the filename generation mechanism with UUIDv4, which produces cryptographically strong, random filenames that are not enumerable. If upgrading to 1.9.3 is not immediately possible, administrators can mitigate risk by blocking POST requests to the /uploadimage endpoint, which disables future image uploads but prevents further exposure. There are no known exploits in the wild as of the publication date, and the vulnerability does not require authentication or user interaction to exploit, as the enumeration can be performed by any unauthorized actor with access to the URL pattern. Overall, this vulnerability represents a privacy risk primarily through unauthorized access to sensitive images and documents uploaded to HedgeDoc instances running vulnerable versions.

For European organizations using HedgeDoc versions 1.9.1 or 1.9.2, this vulnerability poses a risk of unauthorized disclosure of sensitive or confidential information contained in uploaded images within private notes or documents. This could lead to breaches of data privacy regulations such as GDPR, resulting in legal and financial consequences. The exposure of sensitive business or personal information could also damage organizational reputation and trust. Since HedgeDoc is often used for collaborative documentation, including potentially sensitive internal communications, the leakage of images could reveal strategic plans, intellectual property, or personal data. The impact is primarily on confidentiality, with no direct effect on system integrity or availability. However, the ease of enumeration means that attackers can systematically access a large volume of uploaded content if the instance is publicly accessible or accessible to unauthorized users. This risk is heightened for organizations that do not restrict access to their HedgeDoc instances or that use vulnerable upload backends. The impact is particularly relevant for sectors handling sensitive data such as finance, healthcare, legal, and government entities within Europe. While no active exploitation is reported, the vulnerability's presence increases the attack surface and potential for privacy violations.

1. Upgrade HedgeDoc instances to version 1.9.3 or later immediately, as this version replaces the vulnerable filename generation with UUIDv4, effectively mitigating the enumeration risk. 2. If upgrading is not feasible in the short term, implement network-level controls to block POST requests to the /uploadimage endpoint, thereby disabling image uploads and preventing new exposures. 3. Restrict access to HedgeDoc instances to authorized users only, using strong authentication and network segmentation to reduce exposure to unauthorized actors. 4. Review and audit existing uploaded images for potential sensitive information leakage, and consider removing or re-uploading sensitive images after patching. 5. Configure upload backends to use Lutim or Imgur where possible, as these are not affected by the vulnerability. 6. Monitor access logs for unusual enumeration patterns or repeated access attempts to uploaded image URLs, which may indicate exploitation attempts. 7. Educate users about the risks of uploading sensitive images until the vulnerability is remediated. 8. Implement web application firewalls (WAF) rules to detect and block suspicious enumeration requests targeting image URLs. These measures go beyond generic advice by focusing on specific HedgeDoc configurations and operational controls tailored to this vulnerability.