CVE-2026-19863 in Jetty
Summary
by MITRE • 10/15/2026
An unauthenticated client may access certain protected resources when using EthereumAuthenticator if the request path contains the configured login path.
This is caused by the authenticator using an unanchored substring match when identifying the login page. If the login path appears later within a protected request path, the request may be treated as the login page and its authentication or role requirement replaced with ALLOWED.
Exploitation requires the protected resource path to contain the configured login path as a later segment. Explicitly FORBIDDEN routes are not affected.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability identified in EthereumAuthenticator represents a critical flaw in how the library handles URL routing and authentication enforcement, specifically stemming from an improper string matching algorithm used for route identification. The core technical issue lies in the use of an unanchored substring match rather than a strict path prefix or exact match when determining whether a request corresponds to the configured login endpoint. In secure web application frameworks, authentication middleware typically needs to distinguish between public-facing endpoints like login pages and protected resources that require valid credentials. By relying on a simple substring search for the login path within the entire request URI, the authenticator fails to respect URL hierarchy boundaries. This means that if an attacker constructs a malicious request where the configured login path appears as a suffix or embedded segment of a protected resource's URL, the middleware incorrectly classifies this sensitive endpoint as the public login page. Consequently, the authentication and role-based access control checks are bypassed, and the request is granted ALLOWED status without verifying any Ethereum signatures or user credentials.
From an operational perspective, this flaw allows unauthenticated clients to access resources that should be strictly protected by design. For example, if a system configures /auth/login as its login path, a request directed at /api/users/delete?path=/auth/login would likely bypass authentication checks because the substring auth/login is present in the URI. This effectively neutralizes the security controls intended for those specific endpoints, exposing sensitive data or administrative functions to unauthorized access. The impact is particularly severe in applications where certain paths handle critical operations such as user management, financial transactions, or configuration changes. Since the vulnerability relies on path manipulation rather than complex cryptographic attacks, it can be exploited with minimal effort using standard HTTP clients, making it a high-risk issue for any application relying on this authenticator for security enforcement.
It is important to note that explicitly FORBIDDEN routes remain unaffected by this flaw, as their configuration likely overrides the substring matching logic or uses a different validation mechanism that does not rely on path containment checks. However, the existence of even one bypassable protected route undermines the overall integrity of the application's security posture. This type of vulnerability is commonly categorized under CWE-284 Improper Access Control and aligns with ATT&CK technique T1078 Valid Accounts if an attacker uses it to escalate privileges or access data they should not have, although in this specific case, no valid account is required due to the complete bypass. The root cause is a classic example of path traversal logic errors where developers assume that string inclusion implies semantic equivalence between two different URL structures.
To mitigate this vulnerability, immediate remediation involves updating EthereumAuthenticator or implementing a custom middleware layer that enforces strict path matching rules. Developers should ensure that route identification uses anchored prefix checks (e.g., startsWith) rather than substring searches to prevent false positives where the login path appears later in the URI. Additionally, adopting a whitelist approach for public endpoints and ensuring all other paths default to requiring authentication can further reduce the attack surface. Regular security audits focusing on URL parsing logic are recommended to identify similar flaws in routing configurations across the application stack.