SB20260420115 - Multiple vulnerabilities in Istio

Description

This security bulletin contains information about 2 vulnerabilities.

1) Protection Mechanism Failure (CVE-ID: CVE-2026-31837)

CWE-ID: CWE-693 - Protection Mechanism Failure

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Green

The vulnerability allows a remote attacker to disclose sensitive information.

The vulnerability exists due to improper handling of jwks resolver failures in jwks resolver handling when the jwks resolver becomes unavailable or a fetch fails. A remote attacker can trigger jwks resolver failure conditions to disclose sensitive information.

Hardcoded default keys may be exposed regardless of use of the RequestAuthentication resource.

2) Improper access control (CVE-ID: CVE-2026-31838)

CWE-ID: CWE-284 - Improper Access Control

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Green

The vulnerability allows a remote attacker to disclose sensitive information.

The vulnerability exists due to improper access control in Envoy RBAC header matching when handling requests with multiple HTTP header values. A remote attacker can send a specially crafted request with multiple header values to disclose sensitive information.

This may allow unauthorized requests to reach protected services when authorization policies rely on such header-based matching conditions.

Remediation

Install update from vendor's website.

References

• https://github.com/istio/istio/security/advisories/GHSA-v75c-crr9-733c
• https://github.com/istio/istio/security/advisories/GHSA-974c-2wxh-g4ww