CVE-2025-8396 in OSS Server
Summary
by MITRE • 09/15/2025
Insufficiently specific bounds checking on authorization header could lead to denial of service in the Temporal server on all platforms due to excessive memory allocation.This issue affects all platforms and versions of OSS Server prior to 1.26.3, 1.27.3, and 1.28.1 (i.e., fixed in 1.26.3, 1.27.3, and 1.28.1 and later). Temporal Cloud services are not impacted.
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Analysis
by VulDB Data Team • 09/15/2025
The vulnerability identified as CVE-2025-8396 represents a critical denial of service weakness in the Temporal server implementation that stems from inadequate bounds checking within the authorization header processing mechanism. This flaw specifically targets the server's handling of authentication tokens and authorization data, creating a scenario where malicious actors can exploit the system's memory management to trigger excessive resource consumption. The vulnerability affects all platforms and versions of the open source Temporal server software prior to the release versions 1.26.3, 1.27.3, and 1.28.1, indicating that the issue has been present across multiple release streams and affects the core functionality of the distributed workflow platform. The problem manifests when the server processes authorization headers without proper validation of token boundaries, allowing attackers to craft specially formatted requests that cause the system to allocate disproportionately large amounts of memory. This memory allocation behavior directly violates the principles of resource management and input validation that are fundamental to secure software design, creating a pathway for attackers to exhaust available system resources and cause service disruption.
The technical exploitation of this vulnerability occurs through the manipulation of authorization headers in API requests sent to the Temporal server. When the server receives a request containing an authorization header with malformed or excessively sized data, the insufficient bounds checking allows the system to proceed with memory allocation based on the attacker-controlled values. This process can lead to rapid memory consumption that grows exponentially with each malicious request, ultimately resulting in the server becoming unresponsive or crashing entirely. The flaw specifically relates to the server's failure to implement proper input sanitization and validation for authorization tokens, which falls under the broader category of improper input validation as classified by CWE-20. The vulnerability operates at the application layer and can be exploited through standard network protocols, making it particularly dangerous as it requires no specialized tools or conditions beyond sending crafted HTTP requests to the vulnerable service. The memory allocation behavior described in the vulnerability aligns with denial of service attack patterns that are commonly catalogued in the MITRE ATT&CK framework under the technique of resource exhaustion.
The operational impact of CVE-2025-8396 extends beyond simple service disruption to potentially compromise the entire workflow orchestration platform that relies on Temporal server functionality. Organizations using affected versions of Temporal may experience complete service outages, leading to cascading failures in distributed applications that depend on reliable workflow execution. The vulnerability's cross-platform nature means that system administrators must urgently patch all instances regardless of deployment environment, as the flaw exists at the software level rather than being platform-specific. The memory allocation pattern suggests that even a small number of malicious requests could cause significant system degradation, making the attack surface particularly dangerous for high-traffic services. Additionally, the fact that Temporal Cloud services are not impacted indicates that the vulnerability was introduced in the open source implementation but not in the managed cloud offering, highlighting the importance of proper code review and security testing in open source projects. The issue demonstrates how seemingly minor flaws in input validation can have severe consequences for system availability and reliability.
The recommended mitigation strategy for CVE-2025-8396 involves immediate deployment of the patched versions 1.26.3, 1.27.3, and 1.28.1 across all affected Temporal server installations. System administrators should prioritize patching operations and verify that all instances have been successfully updated to prevent exploitation. Organizations should also implement additional monitoring for unusual memory consumption patterns and authorization header processing anomalies as part of their defensive posture. The vulnerability's resolution demonstrates the importance of maintaining current software versions and the critical role of timely security updates in preventing exploitation of known weaknesses. While the immediate fix addresses the core issue, organizations should also consider implementing rate limiting and additional input validation measures to provide defense in depth against similar vulnerabilities. The incident underscores the necessity of robust security testing throughout the software development lifecycle and highlights how input validation flaws can create significant operational risks that extend far beyond the initial vulnerability scope.