CVE-2026-57577 in DotVVM
Summary
by MITRE • 09/14/2026
DotVVM is an open source MVVM framework for web applications. Prior to 4.2.11, 4.3.15, and 5.0.0-preview09-final, a route containing multiple unconstrained parameters in one path segment can cause excessive regular-expression backtracking in DotvvmRoute.IsMatch when a remote requester supplies a long near-match path. DotvvmRouteParser.RouteRegex previously had no matching timeout. Patched runtimes retry with the .NET non-backtracking engine, while runtimes that do not support non-backtracking matching return HTTP 503 after the one-second timeout in DotvvmRoutingMiddleware. This issue is fixed in versions 4.2.11, 4.3.15, and 5.0.0-preview09-final.
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Analysis
by VulDB Data Team • 09/14/2026
DotVVM is an open-source Model-View-ViewModel framework designed for building web applications using ASP.NET Core. A significant security vulnerability exists within the routing mechanism of DotVVM prior to versions 4.2.11, 4.3.15, and 5.0.0-preview09-final. The core issue stems from how the application handles URL path segments containing multiple unconstrained parameters. When a remote attacker supplies a long input string that closely matches but does not perfectly align with the expected route pattern, it triggers excessive regular-expression backtracking within the DotvvmRoute.IsMatch method. This behavior is characteristic of ReDoS, or Regular Expression Denial of Service attacks, where maliciously crafted inputs cause the regex engine to consume disproportionate amounts of CPU resources while attempting to find a match that does not exist in linear time.
The technical root cause lies in the implementation of DotvvmRouteParser.RouteRegex, which previously lacked any matching timeout mechanism. In standard .NET regular expression engines prior to specific updates or configurations, certain patterns with nested quantifiers can exhibit exponential time complexity relative to input length when no match is found. By providing a path segment with multiple unconstrained parameters and appending characters that create near-matches, an attacker forces the engine into deep backtracking states. This results in a single request consuming significant server resources for an extended period, effectively creating a denial of service condition against the application or potentially affecting other processes on the same host due to resource exhaustion.
The operational impact of this vulnerability is primarily availability-related. An attacker can exploit this flaw to degrade performance or completely halt service by sending repeated requests with specifically crafted URLs. This aligns with CWE-400, which describes Uncontrolled Resource Consumption, and maps directly to MITRE ATT&CK technique T1496, Resource Hijacking, where attackers consume resources to disrupt services. The lack of a timeout meant that the server would remain blocked on processing these requests until they were manually terminated or the process crashed, leading to potential downtime for legitimate users relying on the web application.
Mitigation strategies involve upgrading to patched versions of DotVVM, specifically 4.2.11, 4.3.15, and 5.0.0-preview09-final. These updated runtimes address the vulnerability by implementing two distinct protective measures depending on the underlying .NET environment capabilities. For environments that support non-backtracking regular expression engines, the patched code retries matching using this more efficient algorithm, which guarantees linear time complexity regardless of input length. In cases where the runtime does not support non-backtracking matching, the DotvvmRoutingMiddleware is configured to enforce a one-second timeout on route matching operations. If the regex engine exceeds this threshold without finding a match, it aborts processing and returns an HTTP 503 Service Unavailable status code, thereby preventing indefinite resource consumption while still allowing legitimate requests with valid routes to proceed normally.