CVE-2026-118489
Deferred Deferred - Pending Action

Vert.x CachingWebClient Session Data Exposure

Publication date: 2026-11-03

Last updated on: 2026-11-03

Assigner: Eclipse Foundation

Description
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.

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Meta Information

Published
2026-11-03
Last Modified
2026-11-03
Generated
2026-11-03
AI Q&A
2026-11-03
EPSS Evaluated
N/A
NVD
CVE-2026-118489
EUVD
EUVD-2026-115873

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
Eclipse Foundation Eclipse Vert.x 4.0.0
Eclipse Foundation Eclipse Vert.x 5.0.0

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-200 The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
CWE-524 The code uses a cache that contains sensitive information, but the cache can be read by an actor outside of the intended control sphere.

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Executive Summary

This vulnerability affects Eclipse Vert.x versions between 4.0.0-4.5.35 and 5.0.0-5.2.2. It involves the CachingWebClient component improperly sharing user-specific HTTP responses across different users due to a shared cache tier. Responses marked as cacheable but not explicitly marked private or no-store are stored in the shared cache and served to subsequent users requesting the same URL, potentially exposing sensitive data like session cookies or authenticated content.

Detection Guidance

To detect this vulnerability, inspect your Vert.x applications using CachingWebClient for shared cache configurations. Check if responses lack proper cache-control headers like private or no-store. Review logs for repeated identical responses to different users for the same URL.

Impact Analysis

This vulnerability could allow an attacker to receive responses intended for another user, potentially exposing sensitive information such as session cookies or authenticated content. This may lead to session fixation or hijacking attacks, where an attacker gains unauthorized access to a user's session.

Compliance Impact

This vulnerability could lead to unauthorized disclosure of personal or sensitive data, violating privacy requirements under GDPR and HIPAA. Exposure of session cookies or authenticated content may result in non-compliance with data protection regulations, potentially leading to legal and regulatory penalties.

Mitigation Strategies

Upgrade to patched versions: 4.5.36 or later for Vert.x 4.x and 5.2.3 or later for Vert.x 5.x. Ensure cache-control headers are set to private or no-store for user-specific responses. Avoid sharing CachingWebClient across users; use per-user WebClientSession instances.

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