Eclipse Vert.x 4.x/5.x CachingWebClient Shared Cache Disclosure
CVE-2026-118489 Published on November 3, 2026
CachingWebClient shares user-specific HTTP responses across users via the shared cache tier
In Eclipse Vert.x versions [4.0.0,4.5.35] or [5.0.0,5.2.2], when one `CachingWebClient` is shared across users the documented pattern of a per-user `WebClientSession` over a shared caching client a response that is specific to one user but is cacheable and not marked `private`/`no-store` is stored in the client-level shared cache tier and served to other users requesting the same URL. A later user's session, or an anonymous caller through the same client, can receive an earlier user's response. Depending on the response this discloses authenticated content or a session cookie, the latter enabling session fixation or hijacking.
Vulnerability Analysis
CVE-2026-118489 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality, with no impact on integrity and availability.
Weakness Types
What is an Information Disclosure Vulnerability?
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
CVE-2026-118489 has been classified to as an Information Disclosure vulnerability or weakness.
Use of Cache Containing Sensitive Information
The code uses a cache that contains sensitive information, but the cache can be read by an actor outside of the intended control sphere. Applications may use caches to improve efficiency when communicating with remote entities or performing intensive calculations. A cache maintains a pool of objects, threads, connections, pages, financial data, passwords, or other resources to minimize the time it takes to initialize and access these resources. If the cache is accessible to unauthorized actors, attackers can read the cache and obtain this sensitive information.
Products Associated with CVE-2026-118489
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Affected Versions
Eclipse Foundation Eclipse Vert.x:- Version 4.0.0, <= 4.5.35 is affected.
- Version 5.0.0, <= 5.2.2 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.