CVE-2026-30837 in elysia
Summary
by MITRE • 03/10/2026
Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-server communication. Prior to 1.4.26 , t.String({ format: 'url' }) is vulnerable to ReDoS. Repeating a partial url format (protocol and hostname) multiple times cause regex to slow down significantly. This vulnerability is fixed in 1.4.26.
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Analysis
by VulDB Data Team • 03/16/2026
The vulnerability identified as CVE-2026-30837 affects the Elysia framework, a typescript-based solution designed for request validation, type inference, OpenAPI documentation, and client-server communication. This framework serves as a comprehensive tool for building robust web applications with strong type safety and automated documentation capabilities. The security issue manifests in version 1.4.26 and earlier releases, specifically within the string validation functionality that handles URL format validation through the t.String({ format: 'url' }) method. The flaw represents a significant concern for applications relying on this framework for input validation, as it creates potential performance degradation and resource exhaustion scenarios.
The technical root cause of this vulnerability lies in the regular expression implementation used for URL validation within the Elysia framework. When processing input strings that match the partial URL format containing protocol and hostname components, the framework employs a vulnerable regex pattern that exhibits exponential backtracking behavior. This occurs when attackers craft malicious input strings that repeat partial URL patterns multiple times, causing the regular expression engine to perform an enormous number of redundant operations. The regex engine must explore numerous potential matches through backtracking, leading to dramatic performance degradation that can escalate to complete system unresponsiveness. This pattern of vulnerability aligns with the common characteristics of Regular Expression Denial of Service (ReDoS) attacks as classified under CWE-1321.
The operational impact of this vulnerability extends beyond simple performance degradation to encompass potential system availability risks and resource exhaustion. Applications utilizing the affected Elysia framework version may experience significant slowdowns or complete service unavailability when processing specially crafted malicious inputs. Attackers can exploit this weakness by submitting carefully constructed URL strings that trigger the exponential backtracking behavior, potentially consuming excessive CPU resources and memory. This makes the vulnerability particularly dangerous in high-traffic environments or systems with limited computational resources where a single malicious request could cause cascading failures. The vulnerability affects the core validation functionality of the framework, meaning any application relying on Elysia's input validation for URL parameters, API endpoints, or user inputs becomes susceptible to this attack vector.
Mitigation strategies for this vulnerability require immediate action to upgrade to Elysia version 1.4.26 or later, which contains the necessary fixes for the regex implementation. Organizations should conduct thorough testing of their applications after applying the update to ensure compatibility and validate that the vulnerability has been properly addressed. Additionally, implementing input validation at multiple layers of the application architecture provides defense-in-depth protection against similar vulnerabilities. Network-level protections such as rate limiting and input sanitization can help reduce the impact of potential attacks while the framework upgrade is being implemented. Security teams should also monitor for similar patterns in other frameworks and libraries that might be susceptible to ReDoS attacks, particularly those implementing custom validation logic using regular expressions. This vulnerability serves as a reminder of the importance of careful regex design and the need for thorough security testing of validation components in web applications. The fix implemented in version 1.4.26 demonstrates the importance of regular security updates and proper vulnerability management in maintaining secure software ecosystems. Organizations should also consider implementing automated vulnerability scanning tools that can detect similar regex patterns in their codebases to prevent future occurrences of such issues.