CVE-2020-15820 in YouTrack
Summary
by MITRE
In JetBrains YouTrack before 2020.2.6881, the markdown parser could disclose hidden file existence.
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Analysis
by VulDB Data Team • 08/09/2020
The vulnerability identified as CVE-2020-15820 affects JetBrains YouTrack versions prior to 2020.2.6881 and represents a significant information disclosure flaw within the application's markdown parsing functionality. This issue stems from improper handling of file references within markdown content, allowing malicious actors to infer the existence of hidden files on the server through carefully crafted markdown input. The vulnerability specifically targets the markdown parser component that processes user-generated content, creating a pathway for unauthorized reconnaissance activities.
The technical implementation of this flaw involves the markdown parser's inadequate validation of file paths and references when processing user input. When users submit markdown content containing file references or links, the parser fails to properly sanitize or validate these inputs, potentially exposing the underlying filesystem structure. This occurs because the parser does not adequately distinguish between legitimate file access requests and attempts to probe for hidden files, leading to inconsistent responses that reveal file existence information. The vulnerability manifests when the system provides different error messages or response behaviors based on whether a file exists or not, creating a side-channel information leak.
From an operational perspective, this vulnerability poses a serious risk to organizations using JetBrains YouTrack for project management and collaboration. Attackers could leverage this flaw to map the server's filesystem structure, identifying sensitive files, configuration data, or hidden directories that should remain private. The impact extends beyond simple information disclosure as it enables more sophisticated attacks, including privilege escalation attempts and targeted exploitation of other system vulnerabilities. Security researchers have classified this as a medium to high severity issue due to its potential for enabling further attacks and the relatively low effort required to exploit it.
Organizations should immediately update their JetBrains YouTrack installations to version 2020.2.6881 or later to remediate this vulnerability. Additionally, implementing input validation and sanitization measures for markdown content can provide additional defense-in-depth. The vulnerability aligns with CWE-200, Information Exposure, and can be mapped to ATT&CK technique T1083, File and Directory Discovery, as it enables attackers to enumerate system resources. Security teams should also consider implementing network monitoring to detect unusual patterns of file access attempts that might indicate exploitation attempts. Regular security assessments of markdown processing components and input validation mechanisms should be conducted to prevent similar vulnerabilities from emerging in other applications.