# CVE-2026-118489: CachingWebClient shares user-specific HTTP responses across users via the shared cache tier

Status: published. Published: 2026-11-03. Updated: 2026-11-03.

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.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Eclipse Foundation / Eclipse Vert.x: ≥ 4.0.0; ≤ 4.5.35 (affected, semver); ≥ 5.0.0; ≤ 5.2.2 (affected, semver). Source: CNA: eclipse

## Severity and prioritization

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N; source: CNA: eclipse

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-200, CWE-524

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/vert-x3/vertx-web/security/advisories/GHSA-xh2g-9hw9-mvp3 (CNA: eclipse)

- https://gitlab.eclipse.org/security/cve-assignment/-/work_items/523 (CNA: eclipse)

## Provenance

- CNA: eclipse: https://www.cve.org/CVERecord?id=CVE-2026-118489; retrieved 2026-11-03; source updated 2026-11-03

Revision: 9a492660a06b3837ee3a8374f9ba46e99fb0677d3e84deede8c537ad8fc8b817

Canonical: https://y2.dev/cve/CVE-2026-118489

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.