CVE-2026-31838 Auth bypass in istio
Attackers can bypass Istio authorization policies by crafting requests with multiple HTTP header values, allowing unauthorized access to protected services.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-31838?
CVE-2026-31838 is a medium-severity authentication bypass vulnerability in istio, published on 10 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-863
Which versions are affected by CVE-2026-31838?
It affects 1 product.
Products include Istio Istio.
How do I fix CVE-2026-31838?
Upgrade to a fixed version.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-31838 being exploited?
There is no known exploitation of CVE-2026-31838 in the wild and no public exploit code.
Other vulnerabilities in istio
- CVE-2021-31921 Missing authorization in n/a
- CVE-2021-34824 Information disclosure in n/a
- CVE-2026-31837 Istio JWKS resolver to prevent private key material from being exposed when JWKS fetch fails.
- CVE-2021-39155 Authorization Policy Bypass Due to Case Insensitive Host Comparison
- CVE-2021-39156 Fragments in Path May Lead to Authorization Policy Bypass
Sources
Also known as CLEANSTART-2026-WL80869, GHSA-974c-2wxh-g4ww, MINI-24q2-57pm-6v2h, MINI-37wr-554w-896r, MINI-5289-c532-2c86, MINI-5549-qf3g-q56g and 12 more.