Auth bypass in Istio
CVE-2026-39350
Istio is an open platform to connect, manage, and secure microservices. In versions 1.25.0 through 1.27.8, 1.28.0 through 1.28.5, 1.29.0, and 1.29.1, the serviceAccounts and notServiceAccounts fields in AuthorizationPolicy incorrectly interpret dots (.) as a regular expression matcher. Because . is a valid character in a service account name, an AuthorizationPolicy ALLOW rule targeting a service account such as cert-manager.io also matches cert-manager-io, cert-managerXio, etc. A DENY rule targeting the same name fails to block those variants. Fixes are available in versions 1.29.2, 1.28.6, and 1.27.9.
EPSS: 0.002 (11.3th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N.
Affected products
- Istio — versions >= 1.25.0, < < 1.27.9, >= 1.28.0, < 1.28.6, >= 1.29.0, < 1.29.2
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-39350?
- CVE-2026-39350 is a medium-severity vulnerability in Istio, classified under Incorrect Regular Expression. CVSS score: 5.4/10. Published 2026-04-15.
- How severe is CVE-2026-39350?
- Medium severity. CVSS v3 base score is 5.4 out of 10.