CVE-2026-102460 in Vert.x
Summary
by MITRE • 10/15/2026
In Eclipse Vert.x versions [4.0.0, 4.5.34] or [5.0.0,5.0.12] or [5.1.0,5.1.9] or [5.2.0, 5.2.0], a scope bypass vulnerability exists in Eclipse Vert.x Web's ChainAuthHandler when used with scope-requiring authentication handlers such as JWTAuthHandler or OAuth2AuthHandler. When a user is already authenticated on the routing context by a preceding handler in the request pipeline, ChainAuthHandler skips all scope validation configured via withScope() or withScopes(). This affects both any() and all() chain modes.
The root cause is that postAuthentication() relies on internal state that is only set during the authenticate() phase, which is skipped entirely for pre-authenticated users. In any() mode, the absence of this state causes the method to fall through without delegating scope checks to any handler. In all() mode, scope checks are unconditionally skipped.
This allows a user with a valid token but insufficient scopes to access resources protected by scope requirements, provided they were authenticated by an earlier handler in the pipeline. The most common trigger is overlapping authentication handlers on nested routes, where a parent route authenticates broadly and a child route uses a chain to enforce specific scopes.
The impacted component Maven coordinate is io.vertx:vertx-web
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Analysis
by VulDB Data Team • 10/15/2026
Eclipse Vert.x versions spanning from 4.0.0 through 5.2.0 contain a critical authentication scope bypass vulnerability within the ChainAuthHandler component of the vertx-web module. This flaw specifically impacts scenarios where developers utilize chained authentication handlers to enforce granular access control based on user scopes or roles, such as JWTAuthHandler or OAuth2AuthHandler. The vulnerability arises from an incorrect assumption regarding the state of the routing context when a request has already been authenticated by a preceding handler in the pipeline. Instead of validating that the current token possesses the required permissions for the specific resource being accessed, the framework erroneously assumes that prior authentication is sufficient to satisfy all subsequent security constraints defined within the chain.
The technical root cause lies in the implementation of the postAuthentication method within ChainAuthHandler. This method relies on internal state variables that are initialized exclusively during the authenticate phase of a handler's lifecycle. When a request arrives and has already been authenticated by an earlier handler, the framework skips the authentication phase for subsequent handlers to optimize performance. However, this optimization inadvertently bypasses the initialization of critical scope validation logic. In any mode, where only one handler in the chain needs to succeed, the absence of required state causes the method to fall through without delegating scope checks to any available handler. Similarly, in all mode, which requires every handler in the chain to pass its security checks, the scope validations are unconditionally skipped because the necessary preconditions for executing those checks were never met due to the skipped authentication phase.
This architectural flaw results in a severe authorization bypass that allows users with valid but insufficiently scoped tokens to access protected resources. An attacker who possesses a legitimate token lacking specific scopes can exploit this behavior by ensuring their request is authenticated by an earlier, broader handler before reaching the chained endpoint requiring stricter permissions. This scenario commonly occurs in nested route configurations where parent routes apply general authentication while child routes attempt to enforce fine-grained scope restrictions using ChainAuthHandler. The vulnerability effectively nullifies the intended security boundary between different levels of access control within the application architecture.
From a classification perspective, this issue aligns with CWE-285 Improper Authorization and CWE-798 Use of Hard-coded Credentials if interpreted as relying on implicit trust rather than explicit verification. In terms of attack vectors, it corresponds to MITRE ATT&CK technique T1078 Valid Accounts, specifically the aspect of abusing existing valid credentials to escalate privileges or access unauthorized data by bypassing authorization checks. The impact is significant for applications that rely on Vert.x Web for securing API endpoints with role-based or scope-based access control mechanisms.
To mitigate this vulnerability, organizations must upgrade Eclipse Vert.x to version 4.5.35 or later if using the 4.x branch, or version 5.0.13 or later for the 5.0 series, and ensure that any usage of versions in the 5.1 or 5.2 ranges is updated to their respective patched releases which correct the state initialization logic within ChainAuthHandler. For applications unable to upgrade immediately due to dependency constraints, a temporary workaround involves restructuring route definitions to avoid overlapping authentication handlers on nested routes where scope validation is critical. Alternatively, developers can implement custom authorization checks after the routing phase completes but before business logic execution, explicitly verifying scopes against the authenticated principal rather than relying solely on handler chains for enforcement. Regular security audits of Vert.x application architectures should also be conducted to identify similar patterns of implicit trust in authentication states across different handlers.