CVE-2019-20102 in Confluence Server
Summary
by MITRE
The attachment-uploading feature in Atlassian Confluence Server from version 6.14.0 through version 6.14.3, and version 6.15.0 before version 6.15.5 allows remote attackers to achieve stored cross-site- scripting (SXSS) via a malicious attachment with a modified `mimeType` parameter.
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Analysis
by VulDB Data Team • 06/01/2024
The vulnerability CVE-2019-20102 represents a critical stored cross-site scripting flaw in Atlassian Confluence Server affecting versions 6.14.0 through 6.14.3 and 6.15.0 through 6.15.4. This vulnerability resides within the attachment uploading functionality, which serves as a core collaboration feature in Confluence. The flaw enables remote attackers to execute malicious scripts in the context of other users who view the compromised attachments, creating a persistent security risk that can affect multiple users within the same Confluence instance. The vulnerability is categorized under CWE-79 as a failure to sanitize user input, specifically in the handling of attachment metadata.
The technical exploitation mechanism involves modifying the `mimeType` parameter of a malicious attachment during the upload process. When Confluence processes this modified attachment, it fails to properly validate or sanitize the `mimeType` value, allowing attackers to inject malicious JavaScript code that gets stored within the system. This stored payload executes whenever legitimate users access the attachment page, making it a persistent threat that can affect any user who views the compromised content. The vulnerability is particularly dangerous because it leverages the legitimate attachment upload functionality, making it harder to detect and block through traditional security measures.
The operational impact of this vulnerability extends beyond simple XSS attacks, as it can enable attackers to perform various malicious activities including session hijacking, data exfiltration, and privilege escalation within the Confluence environment. Attackers can craft attachments that redirect users to malicious sites, steal cookies, or execute arbitrary code in the context of authenticated users. This vulnerability affects organizations using Confluence Server deployments where users have upload privileges, potentially compromising the entire collaboration platform and any sensitive information stored within it. The stored nature of the vulnerability means that once an attacker successfully uploads a malicious attachment, the threat persists until the attachment is removed or the system is patched.
Organizations should immediately apply the vendor-provided patches for Confluence Server versions 6.14.4 and 6.15.5, which address the input validation issue in the attachment handling code. Security teams should implement network-level monitoring to detect suspicious attachment uploads and consider restricting attachment upload capabilities for untrusted users. The vulnerability aligns with ATT&CK technique T1566.001 for initial access through spearphishing attachments, and T1059.007 for command and control through script-based payloads. Additionally, implementing Content Security Policy headers and regular security scanning of uploaded attachments can provide additional defense-in-depth measures against similar vulnerabilities. Organizations should also conduct security awareness training for users to recognize potentially malicious attachment uploads and maintain comprehensive backup and recovery procedures to address potential exploitation incidents.