CVE-2026-118489
Description
A flaw was found in Eclipse Vert.x Web Client. When a caching client is shared across multiple user sessions, responses intended for a specific user that are not explicitly marked as private are stored in a shared cache. Consequently, an unauthorized user or caller requesting the same resource can receive the previously cached response, leading to sensitive information disclosure. This flaw can expose authentication cookies or confidential user data, potentially enabling session hijacking.
Statement
Red Hat has evaluated this vulnerability as having an Important severity impact because it allows unauthenticated or unauthorized remote callers to access sensitive cached responses across separate sessions without requiring elevated privileges. The flaw manifests in multi-tenant environments where client-side HTTP caching is enabled on a shared client instance, permitting sensitive data such as authentication credentials or personalized replies to be served to subsequent users. Applications that do not share caching web client instances between users or that communicate with services enforcing non-cacheable response headers remain unaffected.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
--- CME Mitigation Guidance (2026-11-04) ---
Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.
The highest-value action is to avoid sharing a single CachingWebClient instance across multiple user WebClientSession instances in multi-tenant application workflows: upgrade to io.vertx:vertx-web-client 4.5.36, 5.2.3 (or the corresponding fixed Red Hat builds), which prevents CacheInterceptor from caching user-specific HTTP responses into the shared client cache tier across distinct user sessions, closing all 2 injection vectors (cross-session shared HTTP cache retrieval, unauthenticated request to previously accessed resource URL). Until patched, this is a concern on Multi-tenant applications sharing an Eclipse Vert.x CachingWebClient across multiple user WebClientSession instances, so Ensure origin services return explicit private or no-store Cache-Control headers on sensitive responses, and isolate CachingWebClient instances per user session. These controls limit blast radius and contain exploitation, but they do not fix the underlying shared client-side HTTP cache information disclosure defect — apply the upstream patch to fully remediate.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | None | N/A | None |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data
If the cache is accessible to unauthorized actors, attackers can read the cache and obtain this sensitive information.
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