CVE-2025-54363 in Knack
Summary
by MITRE • 08/20/2025
Microsoft Knack 0.12.0 allows Regular expression Denial of Service (ReDoS) in the knack.introspection module (issue 1 of 2).
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Analysis
by VulDB Data Team • 09/01/2025
The vulnerability identified as CVE-2025-54363 represents a regular expression denial of service flaw within Microsoft Knack version 0.12.0, specifically affecting the knack.introspection module. This type of vulnerability falls under the broader category of denial of service attacks where malicious input can cause excessive computational overhead through poorly constructed regular expressions. The issue manifests when the system processes user-supplied input that contains crafted regular expression patterns designed to exploit backtracking behavior in the underlying regex engine. Such vulnerabilities are particularly dangerous in web applications as they can be triggered by simple HTTP requests and can consume significant system resources leading to service unavailability.
The technical flaw resides in how the knack.introspection module handles input validation and regular expression processing. When malicious regular expressions are passed through this module, the regex engine enters into a state of exponential backtracking where it repeatedly tries different combinations of matches, causing the system to consume increasing amounts of CPU time and memory. This behavior is characteristic of ReDoS vulnerabilities and can be exploited by attackers to cause system resource exhaustion. The vulnerability is classified as CWE-1321, which specifically addresses regular expression denial of service flaws, and aligns with ATT&CK technique T1499.004 for resource exhaustion attacks. The impact is particularly severe because the vulnerability exists in a module that likely handles introspection operations, which are fundamental to application functionality and may be triggered during normal operational procedures.
Operationally, this vulnerability creates significant risk for systems utilizing Microsoft Knack 0.12.0 as attackers can craft malicious payloads that will cause the application to become unresponsive or crash entirely. The attack surface is broad since introspection modules typically process input from multiple sources including API calls, user interfaces, and configuration files. The computational overhead from ReDoS attacks can escalate rapidly, potentially causing cascading failures in systems where Knack is integrated with other services. Organizations may experience service degradation or complete outages, particularly during peak usage periods when system resources are already constrained. The vulnerability's impact extends beyond simple denial of service as it can also provide attackers with opportunities to perform additional reconnaissance or potentially escalate privileges if the system is not properly isolated.
Mitigation strategies for CVE-2025-54363 should focus on immediate patching of the affected Microsoft Knack version to the latest available release that contains fixes for the regular expression processing. Organizations should implement input validation and sanitization measures to prevent malicious regular expressions from reaching the vulnerable module, including rate limiting and maximum input length restrictions. Network-level protections such as web application firewalls can help detect and block suspicious patterns before they reach the vulnerable code. Additionally, implementing proper monitoring and alerting for unusual CPU and memory usage patterns can help identify exploitation attempts. Security teams should also consider implementing principle of least privilege access controls and isolating the Knack application from critical system components to limit the potential impact of successful exploitation attempts. The remediation process should include thorough testing of patched versions to ensure that the fix does not introduce regressions in legitimate functionality while maintaining the system's overall security posture.