CVE-2026-47836 in Spring Cloud Config
Summary
by MITRE • 08/26/2026
The base directory (spring.cloud.config.server.svn.basedir) used by the Spring Cloud Config Server to clone SVN repositories to is susceptible to time-of-check-time-of-use (TOCTOU) attacks. Spring Cloud Config 5.0.0 - 5.0.4 Spring Cloud Config 4.3.0 - 4.3.4 Spring Cloud Config 4.0.0 - 4.2.8 Spring Cloud Config 3.1.14 and earlier
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Analysis
by VulDB Data Team • 08/26/2026
The vulnerability identified in the specified versions of Spring Cloud Config Server represents a critical security flaw rooted in improper synchronization during file system operations, specifically affecting the configuration management process for Subversion repositories. The core issue lies within the handling of the base directory parameter, spring.cloud.config.server.svn.basedir, which serves as the local working copy location where SVN repository data is cloned and managed by the server. This component is susceptible to a time-of-check-time-of-use attack, commonly referred to as TOCTOU or race condition vulnerability. In this scenario, an attacker can exploit the gap between the moment the system checks for the existence or properties of a file or directory and the subsequent action taken based on that check. By manipulating the filesystem state during this narrow window, it is possible to bypass intended security controls or redirect operations to unintended locations.
From a technical perspective, the flaw arises because the application does not atomically verify and utilize resources when interacting with the local SVN working copy. When Spring Cloud Config Server attempts to clone an SVN repository into the configured base directory, it performs checks to ensure the path is valid and safe before proceeding with write operations. However, these checks are not performed in a manner that guarantees consistency throughout the entire operation sequence. An attacker who has access to the filesystem or can influence its state through other means within the same execution context can alter files or directories between the check phase and the use phase. This allows for potential directory traversal attacks where an adversary might trick the server into writing sensitive configuration data outside of the intended sandboxed area, potentially overwriting critical system files or injecting malicious content that will be served to clients upon subsequent requests.
The operational impact of this vulnerability is severe, particularly in environments where Spring Cloud Config Server manages sensitive application configurations such as database credentials, API keys, and internal service endpoints. If an attacker successfully exploits the TOCTOU race condition, they may achieve arbitrary file write capabilities on the host system running the server. This can lead to remote code execution if the written files are later processed by other components or interpreted in a way that allows command injection. Furthermore, it compromises the integrity of the configuration management pipeline, allowing for data tampering where attackers could inject malicious configurations into applications connected to this central config server. Such manipulation could result in widespread service disruption, unauthorized access to backend systems, or complete compromise of the microservices architecture relying on Spring Cloud Config for dynamic property resolution.
This vulnerability aligns with CWE-367, which describes time-of-check-time-of-use race conditions, and falls under MITRE ATT&CK technique T1059, specifically Command Scripting if exploitation leads to code execution, or T1482 regarding configuration discovery and modification in cloud environments. The risk is exacerbated by the fact that Spring Cloud Config Server often runs with elevated privileges relative to application containers, making successful exploitation more likely to result in significant system compromise rather than isolated service degradation.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. The primary recommendation is to upgrade Spring Cloud Config to a version where this race condition has been addressed by the development team, ensuring that file operations are performed atomically or with proper locking mechanisms to prevent concurrent modification during critical checks. For environments unable to immediately patch, administrators should restrict filesystem permissions so that the process running Spring Cloud Config Server cannot write outside of its designated working directory using strict chroot jails or containerized isolation techniques like Docker security profiles. Additionally, input validation for the base directory path should be enforced at multiple layers to prevent traversal sequences from being processed even if race conditions are attempted. Regular auditing of filesystem access logs can also help detect attempts to exploit this vulnerability by monitoring for unusual patterns in file creation or modification within the SVN working copy directories.