Vulnerability Description
Istio is an open platform to connect, manage, and secure microservices. Prior to 1.29.1, 1.28.5, and 1.27.8, a vulnerability in Envoy RBAC header matching could allow authorization policy bypass when policies rely on HTTP headers that may contain multiple values. An attacker could craft requests with multiple header values in a way that causes Envoy to evaluate the header differently than intended, potentially bypassing authorization checks. This may allow unauthorized requests to reach protected services when policies depend on such header-based matching conditions. This vulnerability is fixed in 1.29.1, 1.28.5, and 1.27.8.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Istio | Istio | < 1.27.8 |
Related Weaknesses (CWE)
References
- https://github.com/istio/istio/commit/004fd6921314a8e2293fd195d91645dcbbff0aa1
- https://github.com/istio/istio/security/advisories/GHSA-974c-2wxh-g4wwVendor Advisory
FAQ
What is CVE-2026-31838?
CVE-2026-31838 is a vulnerability with a CVSS score of 5.3 (MEDIUM). Istio is an open platform to connect, manage, and secure microservices. Prior to 1.29.1, 1.28.5, and 1.27.8, a vulnerability in Envoy RBAC header matching could allow authorization policy bypass when ...
How severe is CVE-2026-31838?
CVE-2026-31838 has been rated MEDIUM with a CVSS base score of 5.3/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-31838?
Check the references section above for vendor advisories and patch information. Affected products include: Istio Istio.