CVE-2025-66382 identifies a vulnerability in the libexpat XML parsing library, versions through 2.7.3, caused by inefficient algorithmic complexity (CWE-407). The issue arises when libexpat processes a crafted XML file approximately 2 MiB in size, which triggers excessive computational effort, causing the parser to consume dozens of seconds processing the input. This behavior can lead to a denial-of-service (DoS) condition by exhausting CPU resources, potentially impacting availability of applications or services relying on libexpat for XML parsing. The vulnerability does not affect confidentiality or integrity, as it does not allow data leakage or unauthorized modification. The CVSS 3.1 score is 2.9 (low), reflecting the requirement for local access (AV:L), high attack complexity (AC:H), no privileges (PR:N), and no user interaction (UI:N). No known exploits exist in the wild, and no official patches have been released at the time of publication. The vulnerability is primarily a performance degradation issue rather than a direct security compromise. Libexpat is widely used in various open-source and commercial software for XML parsing, including embedded systems, network devices, and server applications. Attackers with local access could exploit this by supplying crafted XML files to trigger prolonged processing times, potentially disrupting service availability.

For European organizations, the primary impact of CVE-2025-66382 is potential denial-of-service through resource exhaustion when processing maliciously crafted XML files. This can degrade performance or cause service interruptions in applications relying on libexpat, such as web servers, middleware, or embedded devices. Critical infrastructure sectors using XML-based communication or configuration may experience reduced availability, affecting operational continuity. Although the vulnerability requires local access and has high attack complexity, insider threats or compromised internal systems could exploit it. The lack of confidentiality or integrity impact limits data breach risks, but availability degradation can still disrupt business processes. Organizations with high XML processing workloads or automated XML ingestion pipelines are more susceptible. The absence of known exploits reduces immediate risk, but the vulnerability should be addressed proactively to maintain service reliability.

To mitigate CVE-2025-66382, organizations should implement several specific measures beyond generic advice: 1) Monitor and restrict the size of XML inputs accepted by applications using libexpat to prevent processing of unusually large or suspicious files. 2) Employ input validation and XML schema validation to reject malformed or unexpected XML content before parsing. 3) Isolate XML parsing operations in sandboxed or resource-limited environments to contain potential resource exhaustion impacts. 4) Apply rate limiting on XML processing requests to reduce the risk of denial-of-service from repeated crafted inputs. 5) Stay informed on libexpat project updates and apply patches promptly once available. 6) Conduct code audits and testing to identify and remediate inefficient XML processing patterns in dependent software. 7) For critical systems, consider alternative XML parsers with better resilience to algorithmic complexity issues until libexpat patches are released.