CVE-2025-54363 is a vulnerability identified in Microsoft Knack version 0.12.0, specifically within the knack.introspection module. The issue arises from an inefficient regular expression pattern used in the function extract_full_summary_from_signature: "\s(:param)\s+(.+?)\s:(.*)". This pattern is vulnerable to catastrophic backtracking when processing specially crafted docstrings that contain a large amount of whitespace without a terminating colon. An attacker who has the capability to inject or control docstring content in applications using this module can exploit this flaw to trigger a Regular Expression Denial of Service (ReDoS) attack. The attack causes excessive CPU consumption, leading to degraded performance or potential service outages. Microsoft Knack is utilized by Azure CLI, which is widely used for managing Azure cloud resources. The vulnerability has a CVSS 4.0 base score of 6.9, categorized as medium severity, with an attack vector of local (AV:L), low attack complexity, no privileges or user interaction required, and a high impact on availability. No known exploits are currently reported in the wild, and no patches have been released as of the publication date (August 20, 2025).

For European organizations, the impact of this vulnerability can be significant, especially for those heavily reliant on Azure cloud services and automation via Azure CLI. Exploitation could lead to denial of service conditions on systems running affected versions of Microsoft Knack, potentially disrupting cloud management operations, automation workflows, and administrative tasks. This could result in operational delays, increased resource consumption, and potential cascading effects on dependent services. Since the attack requires local access or the ability to inject docstring content, the threat is more pronounced in environments where untrusted code or inputs are processed without sufficient validation. Organizations using custom scripts or third-party tools that incorporate Microsoft Knack may also be at risk. The availability impact could affect critical cloud infrastructure management, leading to downtime or degraded service levels.

To mitigate this vulnerability, European organizations should: 1) Immediately audit their environments to identify usage of Microsoft Knack 0.12.0, particularly within Azure CLI or any custom tooling. 2) Restrict or sanitize any input that could influence docstring content processed by the knack.introspection module to prevent injection of maliciously crafted strings. 3) Implement resource limits and monitoring on CPU usage for processes running Azure CLI or related tools to detect abnormal consumption patterns indicative of ReDoS attacks. 4) Apply strict access controls to limit who can execute or modify scripts that utilize Microsoft Knack, reducing the risk of local exploitation. 5) Monitor vendor communications for patches or updates addressing this vulnerability and plan prompt deployment once available. 6) Consider isolating or sandboxing environments where untrusted code or inputs are processed to contain potential impact. 7) Educate developers and administrators about the risks of ReDoS and encourage secure coding practices around regular expressions.