Improper Certificate Validation in Cilium - CVE-2026-83620
Published: November 9, 2026
Vulnerability identifier: #VU162617
CSH Severity: Low
CVSS v4: 7 [CVSS:4.0/AV:A/AC:L/AT:N/PR:L/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-83620
CWE-ID: CWE-295
Exploitation vector: Adjecent network
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a low-privileged adjacent-network attacker to bypass mutual authentication and impersonate any identity in a Cilium cluster with mutual authentication enabled.
The vulnerability exists due to improper certificate validation in Cilium mutual authentication when processing certificate chains during TLS handshakes. A low-privileged adjacent-network attacker with any valid client certificate can append a target identity's public certificate to their certificate chain and authenticate as that identity.
Affected software
Cilium
How to mitigate CVE-2026-83620
Install security update from vendor's website.
Cilium - addressed in versions 1.17.18, 1.18.12, 1.19.6