CVE-2026-25825 in SignServer
Summary
by MITRE • 09/15/2026
An issue was discovered in Keyfactor SignServer before 7.6.0. The output file to which SignerStatusReportWorker logs the report can be set to any path, even one that points to a file that already exists. This gives a user (with admin access) the possibility to write files in arbitrary directories in the server filesystem and potentially overwrite files accessible by the local user JBoss.
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Analysis
by VulDB Data Team • 09/15/2026
The vulnerability identified in Keyfactor SignServer prior to version 7.6.0 represents a critical file system manipulation flaw rooted in improper validation of user-supplied input regarding output file paths. The specific component affected is the SignerStatusReportWorker, which is responsible for generating and logging status reports related to signing operations. In vulnerable versions, this worker allows an administrator-level user to specify the destination path for these report files without sufficient sanitization or restriction checks. This lack of validation enables the attacker to direct the output stream toward arbitrary locations on the server's file system rather than being confined to a designated log directory.
From a technical perspective, this flaw constitutes a classic case of Path Traversal combined with Arbitrary File Write capabilities. By allowing the configuration of an absolute path or a relative path that escapes the intended sandbox, the application fails to enforce strict boundaries around where data can be written. This behavior aligns directly with CWE-22, which describes Improper Limitation of a Pathname to a Restricted Directory, and CWE-436, which refers to Interpretation Error, as the system misinterprets user-provided paths that may contain directory traversal sequences or point to sensitive configuration files. The ability to write to arbitrary directories effectively grants an attacker with administrative privileges the capacity to overwrite existing files on the server.
The operational impact of this vulnerability is severe due to the privilege level required and the potential for code execution through file overwriting. Since the flaw requires admin access, it primarily poses a risk in scenarios where insider threats are present or when an administrator account has been compromised via other vectors such as credential theft or phishing. Once an attacker gains control of an admin account, they can leverage this vulnerability to overwrite critical files accessible by the local user running JBoss, which is typically the application server process. Overwriting configuration files, startup scripts, or library binaries with malicious content allows for persistent access and potential remote code execution, as the application server may load these modified components during subsequent restarts or runtime operations.
This vulnerability maps to several techniques within the MITRE ATT&CK framework that describe post-exploitation activities aimed at maintaining persistence or escalating privileges. Specifically, it relates to T1530 Data from Information Repositories if used for exfiltration via log manipulation, but more critically aligns with T1222 File and Directory Permissions Modification when altering file attributes to facilitate further attacks, and potentially T1059 Command and Scripting Interpreter if the overwritten files are scripts executed by the system. The ability to write arbitrary files is also a precursor to T1496 Remote Service Availability Disruption or T1578 Cryptographic Protocol Enforcement failures if configuration files controlling security policies are modified.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. The primary solution is to upgrade Keyfactor SignServer to version 7.6.0 or later, where this input validation flaw has been addressed by the vendor. For environments that cannot immediately patch, administrators should implement strict file system permissions using operating-level controls such as SELinux or AppArmor to restrict write access for the JBoss user account outside of designated log directories. Additionally, implementing a Web Application Firewall with rules capable of detecting path traversal sequences in configuration inputs can provide an additional layer of defense. It is also recommended to enforce principle of least privilege by ensuring that administrative accounts are protected with multi-factor authentication and monitored closely for unusual activity patterns indicative of lateral movement or file system manipulation attempts.