CVE-2025-61728 is a denial of service vulnerability in the Go programming language's standard library, specifically in the archive/zip package. The root cause is an inefficient, super-linear time complexity algorithm used for indexing file names within ZIP archives. This indexing process is triggered the first time a file inside a ZIP archive is accessed. An attacker can exploit this by crafting a specially designed ZIP archive with a large or complex set of file names that cause the indexing algorithm to consume excessive CPU and memory resources. This results in a denial of service condition, potentially causing applications or services that rely on Go's archive/zip package to become unresponsive or crash. The vulnerability affects all Go versions up to 1.25.0, with no patches currently available. Although no exploits have been observed in the wild, the vulnerability is significant due to the widespread use of Go in cloud-native applications, microservices, and backend systems that often handle ZIP files. The vulnerability is classified under CWE-407, which relates to inefficient algorithmic complexity leading to performance degradation. This flaw does not require authentication or user interaction beyond processing the malicious ZIP file, increasing its risk profile. The lack of a CVSS score necessitates an independent severity assessment based on impact and exploitability factors.

For European organizations, the primary impact of CVE-2025-61728 is the risk of denial of service in applications and services that use the Go archive/zip package to process ZIP files. This could disrupt business operations, especially for companies relying on automated file ingestion, cloud services, or microservices architectures built with Go. Service outages could affect customer-facing applications, internal tools, or critical infrastructure components, leading to operational downtime and potential financial losses. Additionally, the vulnerability could be leveraged as part of a larger attack chain to degrade service availability or distract security teams. Organizations in sectors such as finance, telecommunications, and government, which often use Go for scalable backend systems, may face increased risk. The absence of known exploits suggests a window for proactive mitigation, but also the need for vigilance as attackers may develop exploits once the vulnerability becomes public knowledge. The impact is compounded by the fact that no patch is currently available, requiring interim defensive measures.

1. Monitor and restrict the size and complexity of ZIP files accepted by applications, implementing strict input validation and file size limits to reduce exposure. 2. Employ resource usage monitoring and alerting on services that process ZIP files to detect abnormal CPU or memory consumption indicative of exploitation attempts. 3. Where possible, sandbox or isolate the processing of ZIP archives to contain potential denial of service effects and prevent cascading failures. 4. Consider implementing timeouts or limits on the duration of ZIP file processing operations to avoid prolonged resource exhaustion. 5. Stay informed on updates from the Go project and apply patches promptly once they become available. 6. For critical systems, evaluate alternative libraries or custom ZIP processing implementations that do not exhibit super-linear complexity. 7. Conduct code reviews and testing focused on archive/zip usage patterns to identify and mitigate potential exploitation vectors. 8. Educate developers and operations teams about the vulnerability and encourage secure coding and deployment practices related to file handling.