CVE-2021-26084 in Confluence Server
Summary
by MITRE • 08/30/2021
In affected versions of Confluence Server and Data Center, an OGNL injection vulnerability exists that would allow an authenticated user, and in some instances an unauthenticated user, to execute arbitrary code on a Confluence Server or Data Center instance. The vulnerable endpoints can be accessed by a non-administrator user or unauthenticated user if ‘Allow people to sign up to create their account’ is enabled. To check whether this is enabled go to COG > User Management > User Signup Options. The affected versions are before version 6.13.23, from version 6.14.0 before 7.4.11, from version 7.5.0 before 7.11.6, and from version 7.12.0 before 7.12.5.
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Analysis
by VulDB Data Team • 02/10/2025
This vulnerability represents a critical OGNL injection flaw in Atlassian Confluence Server and Data Center platforms that enables remote code execution under specific conditions. The vulnerability stems from insufficient input validation within the application's object graph navigation language processing mechanism, allowing attackers to inject malicious OGNL expressions that execute arbitrary commands on the underlying server. The flaw affects multiple version ranges spanning from 6.13.x through 7.12.x, making it particularly widespread across the Confluence product lineage. The vulnerability is classified as a CWE-94 - Improper Control of Generation of Code and falls under the ATT&CK technique T1059.001 - Command and Scripting Interpreter for its code execution capabilities.
The exploitation conditions for this vulnerability require either authenticated access or, in certain configurations, unauthenticated access when the user signup option is enabled. This configuration allows any user to create accounts, which then provides access to vulnerable endpoints that should otherwise be restricted. The attack vector typically involves crafting malicious OGNL expressions through specific API endpoints that process user input without proper sanitization. Security researchers have noted that the vulnerability is particularly dangerous because it can be exploited by non-administrative users, significantly expanding the potential attack surface compared to typical privilege escalation vulnerabilities.
The operational impact of this vulnerability extends beyond simple code execution to encompass full system compromise capabilities. An attacker who successfully exploits this vulnerability can gain complete control over the Confluence server, potentially leading to data exfiltration, persistence mechanisms, lateral movement within the network, and establishment of backdoors. The vulnerability affects both Confluence Server and Data Center editions, meaning organizations with either deployment type are at risk, regardless of their security posture. The affected versions span across several major release lines, indicating that the flaw was present for an extended period and likely exploited in the wild before its disclosure.
Organizations should prioritize immediate patching of all affected versions to remediate this vulnerability, with the specific patch versions being 6.13.23, 7.4.11, 7.11.6, and 7.12.5 respectively. In environments where patching is not immediately possible, administrators should consider implementing network-level restrictions to limit access to vulnerable endpoints and disable the user signup functionality if not required. The vulnerability highlights the importance of proper input validation and the principle of least privilege in web application security. Organizations should also review their access controls and user management configurations to ensure that unnecessary permissions are not granted to users. Additionally, implementing monitoring solutions to detect unusual API activity patterns can help identify potential exploitation attempts. The vulnerability demonstrates the critical need for continuous security assessment and the importance of maintaining current security patches across all enterprise applications.