CVE-2026-59903
MEDIUMDescription
Netty is an asynchronous, event-driven network application framework. Prior to 4.1.137.Final and 4.2.17.Final, io.netty.handler.codec.http.cors.CorsHandler setVaryHeader replaces application Vary headers such as Authorization or Cookie with Origin, allowing a caching proxy or CDN to reuse authenticated responses across users and disclose sensitive information. This issue is fixed in versions 4.1.137.Final and 4.2.17.Final.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 16% of all known CVEs.
References
Related Vulnerabilities
Other CWE-524 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2019-9494 | Medium | 5.9 | 3.9% | - | Fix |
| CVE-2021-24027 | High | 7.5 | 3.8% | - | Fix |
| CVE-2019-9495 | Low | 3.7 | 3.4% | - | Fix |
| CVE-2019-14997 | Medium | 4.3 | 1.2% | - | Fix |
| CVE-2024-0874 | Medium | 5.3 | 0.8% | - | Fix |
| CVE-2024-45596 | High | 7.4 | 0.7% | - | Fix |
Common questions
How do I fix CVE-2026-59903?
No published fix for CVE-2026-59903 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-59903 being actively exploited?
Not that we know of. CVE-2026-59903 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.24% is the estimated probability that it will be exploited in the next 30 days. That is higher than 16% of all scored CVEs.
How severe is CVE-2026-59903?
CVE-2026-59903 has a CVSS v3 base score of 6.5, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-08-17.