Eclipse Vert.x up to 4.5.35/5.2.2 CachingWebClient session fixiation

Summaryinfo

A vulnerability identified as critical has been detected in Eclipse Vert.x up to 4.5.35/5.2.2. This affects an unknown part of the component CachingWebClient. The manipulation leads to session fixiation. This vulnerability is referenced as CVE-2026-118489. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Eclipse Vert.x up to 4.5.35/5.2.2. This issue affects some unknown functionality of the component CachingWebClient. The manipulation with an unknown input leads to a session fixiation vulnerability. Using CWE to declare the problem leads to CWE-384. Authenticating a user, or otherwise establishing a new user session, without invalidating any existing session identifier gives an attacker the opportunity to steal authenticated sessions. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-118489 since 10/28/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 11/03/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Vendor

• Eclipse

Name

• Vert.x

Version

• 4.5.0
• 4.5.1
• 4.5.2
• 4.5.3
• 4.5.4
• 4.5.5
• 4.5.6
• 4.5.7
• 4.5.8
• 4.5.9
• 4.5.10
• 4.5.11
• 4.5.12
• 4.5.13
• 4.5.14
• 4.5.15
• 4.5.16
• 4.5.17
• 4.5.18
• 4.5.19
• 4.5.20
• 4.5.21
• 4.5.22
• 4.5.23
• 4.5.24
• 4.5.25
• 4.5.26
• 4.5.27
• 4.5.28
• 4.5.29
• 4.5.30
• 4.5.31
• 4.5.32
• 4.5.33
• 4.5.34
• 4.5.35
• 5.2.0
• 5.2.1
• 5.2.2

License

• open-source

CPE 2.3info

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CPE 2.2info

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Entryinfo

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