CVE-2026-1002 in Vert.x
Summary
by MITRE • 01/15/2026
The Vert.x Web static handler component cache can be manipulated to deny the access to static files served by the handler using specifically crafted request URI.
The issue comes from an improper implementation of the C. rule of section 5.2.4 of RFC3986 and is fixed in Vert.x Core component (used by Vert.x Web): https://github.com/eclipse-vertx/vert.x/pull/5895
Steps to reproduce Given a file served by the static handler, craft an URI that introduces a string like bar%2F..%2F after the last / char to deny the access to the URI with an HTTP 404 response. For example https://example.com/foo/index.html can be denied with https://example.com/foo/bar%2F..%2Findex.html
Mitgation Disabling Static Handler cache fixes the issue.
StaticHandler staticHandler = StaticHandler.create().setCachingEnabled(false);
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Analysis
by VulDB Data Team • 03/18/2026
The vulnerability identified as CVE-2026-1002 affects the Vert.x Web static handler component, which is widely used for serving static content in web applications built on the Vert.x framework. This security flaw stems from an improper implementation of the canonicalization rules defined in section 5.2.4 of RFC3986, which governs the syntax and semantics of Uniform Resource Identifiers. The issue manifests when the static handler processes request URIs that contain specifically crafted sequences designed to manipulate the file system path resolution. The vulnerability exploits the way the component handles path traversal sequences, particularly the combination of percent-encoded forward slashes and dot-dot segments that should normally be normalized according to RFC3986 standards. This improper handling creates a path traversal condition that allows attackers to craft malicious URIs that bypass normal access controls and result in denial of service through HTTP 404 responses.
The technical implementation flaw occurs within the Vert.x Core component's URI parsing and path resolution logic, which fails to properly canonicalize URI paths before attempting to resolve static file requests. When a malicious URI such as https://example.com/foo/bar%2F..%2Findex.html is processed, the static handler does not correctly normalize the path segments, allowing the crafted sequence to interfere with the intended file access pattern. This vulnerability specifically targets the caching mechanism of the static handler, where the improper path resolution causes the component to fail in locating the requested file, resulting in a 404 error response. The flaw represents a classic path traversal vulnerability that can be classified under CWE-22, Path Traversal, and aligns with ATT&CK technique T1071.004 for application layer protocol manipulation. The issue is particularly concerning because it affects the core static file serving functionality and can be exploited to deny access to legitimate resources, effectively creating a denial of service condition for authorized users.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be leveraged to systematically block access to critical static resources such as CSS files, JavaScript libraries, images, and other essential web assets. Attackers can craft multiple malicious URIs to target different files within the application's static content directory, potentially disrupting the entire user interface or application functionality. The vulnerability affects web applications that rely on Vert.x Web's static handler for serving assets, which includes numerous enterprise applications, microservices, and web APIs. The exploitation requires minimal technical knowledge and can be automated, making it particularly dangerous in environments where static content serves as a critical component of the application's user experience. Organizations using Vert.x Web frameworks without proper mitigations are at risk of experiencing service degradation or complete unavailability of static resources.
The recommended mitigation strategy involves disabling the static handler cache as a temporary workaround, which can be implemented by setting the caching enabled flag to false in the StaticHandler configuration. This approach effectively prevents the vulnerable path canonicalization logic from being triggered during request processing. The permanent solution requires updating to a patched version of Vert.x Core that properly implements RFC3986 canonicalization rules, as demonstrated by the fix referenced in the GitHub pull request. Organizations should also consider implementing additional input validation and sanitization measures at the application level to prevent malicious URI sequences from reaching the static handler component. Security teams should monitor for any potential bypasses or related vulnerabilities in the Vert.x ecosystem and ensure comprehensive testing of static file serving components after applying the fix. The vulnerability highlights the importance of proper URI handling and canonicalization in web frameworks, emphasizing that even seemingly simple components can introduce critical security risks when not properly implemented according to established standards.