Sensitive data exposure via cross-domain cookie injection
Published Jul 14, 2026 · Updated Jul 14, 2026
Origin validation error in Eclipse Vert.x Web Client 4.0.0 through 4.5.29 and 5.0.0 through 5.1.4 allows remote attackers to read request data. The WebClientSession cookie store accepts a Set-Cookie Domain value without verifying that it belongs to the responding host, then sends the cookie to that unrelated domain. Exploitation requires the same session to contact an attacker-controlled server and later a targeted service, where requests run under the attacker's account and expose their payloads.
Summary
What happened
Origin validation error in Eclipse Vert.x Web Client 4.0.0 through 4.5.29 and 5.0.0 through 5.1.4 allows remote attackers to read request data. The WebClientSession cookie store accepts a Set-Cookie Domain value without verifying that it belongs to the responding host, then sends the cookie to that unrelated domain. Exploitation requires the same session to contact an attacker-controlled server and later a targeted service, where requests run under the attacker's account and expose their payloads.
The record
- CVE
- CVE-2026-15076
- Published
- Jul 14, 2026
- Updated
- Jul 14, 2026
- Vendor
- The Eclipse Foundation
- Product
- Eclipse Vert.x
- Classifications
- CWE-346, CAPEC-61
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 14, 2026CVE publishedPublication date reported by the CVE source.
- Jul 14, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=4.0.0 <=4.5.29
- Affected versionversion=5.0.0 <=5.1.4
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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