CachingWebClient shares user-specific HTTP responses across users via the shared cache tier
Affects Eclipse Vert.x 4.0.0 through 4.5.35 and 5.0.0 through 5.2.2 when one CachingWebClient is shared across users. The advisory gives no separate vendor rating. Fixed in 4.5.36 and 5.2.3.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 4.5.36, 5.2.3
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 4.5.36, 5.2.3.
- Exploitation0/40No signal
- Exposure20/25No login or user action needed, CISA rates it automatable · Data gap: Advisories don't say whether default setups are affected
- Reach?/20Reach: unknown (data gap). No tracked technology or package matched
- Severity7.5/10CVSS 7.5
- No patch0/5No signal
What would change the score
- Would score about 73 if added to CISA KEV
- Would score about 68 if CISA's SSVC rates exploitation active
- Would score about 33 if advisories confirm default setups are exposed
CVE-2026-118489 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.5 (high) and affects Eclipse Vert.x; fixed in 4.5.36 and 5.2.3.
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- Published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 28/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Unclear
- Fix
- Fixed in 4.5.36, 5.2.3
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: yes
- Technical impact: partial
Summary
Eclipse Vert.x, specifically its CachingWebClient component, is affected when a single caching client is shared among multiple users. A user's personal web responses can be stored in a shared cache and returned to other users or anonymous callers requesting the same address, potentially exposing private content or session cookies to unauthorized people.
Read the original 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.
What to do
Upgrade to a fixed version: 4.5.36, 5.2.3.
Timeline
- CVE published
- First seen by cve.now
- CISA SSVC assessment
Exploitation: none · Automatable: yes · Technical impact: partial
- Record last updated
Affected versions
- Eclipse Foundation Eclipse Vert.x
From 4.0.0 · through 4.5.35; From 5.0.0 · through 5.2.2
Evidence 2
- Advisory
- Link
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-118489
Is CVE-2026-118489 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
CachingWebClient can store a user-specific HTTP response in a shared cache and then serve it to other users. This can disclose response bodies belonging to one user, and through Set-Cookie headers it can expose session credentials.Source: github.com
Which versions are affected by CVE-2026-118489?
Eclipse Vert.x: from 4.0.0 through 4.5.35; from 5.0.0 through 5.2.2.Source: cve.now feed data
Am I affected, and how do I check?
Eclipse Vert.x 4.0.0 through 4.5.35 and 5.0.0 through 5.2.2 are in the affected ranges. The issue needs a single CachingWebClient shared across user principals, an origin response that is user-specific but cacheable and not marked private or no-store, and a missing restrictive origin directive as a contributing condition. Check the Vert.x version in the project's dependency file.Source: github.com
How do I fix CVE-2026-118489?
Upgrade to Eclipse Vert.x 4.5.36 or 5.2.3, the patched versions for each branch.Source: github.com