CVE-2026-48115 in Misskey
Summary
by MITRE • 08/04/2026
Misskey is an open source, federated social media platform. All Misskey servers running versions 2024.5.0 and later, but prior to 2026.5.4, contain a vulnerability in the Server Announcements API where insufficient permission checks allow attackers to access limited portions of data that they normally couldn't view. This vulnerability occurs whether or not federation is enabled. This issue has been fixed in version 2026.5.4.
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Analysis
by VulDB Data Team • 08/04/2026
The vulnerability identified in Misskey social media platform affects servers running versions between 2024.5.0 and 2026.5.3, representing a critical authorization flaw that undermines the platform's security model. This issue specifically targets the Server Announcements API component, which serves as a mechanism for administrators to communicate important information to users across the federated network. The vulnerability stems from inadequate permission validation within this API endpoint, creating a path for unauthorized access to sensitive data that should remain restricted to authorized personnel. The flaw exists regardless of federation status, meaning it impacts all Misskey deployments whether they participate in the broader federated social network or operate in isolation. This represents a fundamental breakdown in the principle of least privilege that governs secure software design, where proper access controls fail to enforce appropriate data boundaries.
The technical nature of this vulnerability aligns with CWE-284, which describes improper access control mechanisms that allow unauthorized users to gain access to resources they should not be able to reach. The Server Announcements API in Misskey was designed to provide administrative communication capabilities but failed to implement proper authentication checks before exposing sensitive data elements. Attackers could exploit this weakness to retrieve information that typically requires elevated privileges or specific user roles, potentially including system configuration details, user metadata, or other confidential server information. The scope of accessible data remains limited according to the vulnerability description, suggesting the flaw doesn't provide complete system compromise but rather targeted access to specific data segments within the announcements functionality.
From an operational impact perspective, this vulnerability creates significant risk for Misskey deployments since it allows malicious actors to bypass normal access controls and gather information that could aid in further exploitation attempts. The federated nature of Misskey means that compromised servers could potentially be used as entry points to attack other connected instances or users within the network. Security researchers should consider this vulnerability in relation to ATT&CK technique T1078 which covers valid accounts and credential access, as unauthorized individuals gaining access through this flaw could potentially escalate their privileges or use the gathered information for more sophisticated attacks. Organizations running affected versions must immediately implement mitigation strategies while planning upgrades to the patched version 2026.5.4.
The remediation approach for this vulnerability requires immediate deployment of the patched Misskey version 2026.5.4, which implements proper permission checks within the Server Announcements API. System administrators should conduct thorough inventory checks to identify all affected server instances and ensure complete patching across their deployments. Additional security measures include implementing network segmentation to limit access to administrative APIs, monitoring for unusual API access patterns that might indicate exploitation attempts, and reviewing existing access controls for other components of the platform. The vulnerability demonstrates the importance of comprehensive access control testing, particularly for administrative interfaces in federated systems where security failures can propagate across multiple connected instances. This incident underscores the necessity of regular security audits and proper code review processes to prevent similar authorization bypass vulnerabilities in distributed social media platforms.