Vulnerability Description
Istio is an open source platform for providing a uniform way to integrate microservices, manage traffic flow across microservices, enforce policies and aggregate telemetry data. According to [RFC 4343](https://datatracker.ietf.org/doc/html/rfc4343), Istio authorization policy should compare the hostname in the HTTP Host header in a case insensitive way, but currently the comparison is case sensitive. The proxy will route the request hostname in a case-insensitive way which means the authorization policy could be bypassed. As an example, the user may have an authorization policy that rejects request with hostname "httpbin.foo" for some source IPs, but the attacker can bypass this by sending the request with hostname "Httpbin.Foo". Patches are available in Istio 1.11.1, Istio 1.10.4 and Istio 1.9.8. As a work around a Lua filter may be written to normalize Host header before the authorization check. This is similar to the Path normalization presented in the [Security Best Practices](https://istio.io/latest/docs/ops/best-practices/security/#case-normalization) guide.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Istio | Istio | < 1.9.8 |
Related Weaknesses (CWE)
References
- https://datatracker.ietf.org/doc/html/rfc4343Third Party Advisory
- https://github.com/istio/istio/security/advisories/GHSA-7774-7vr3-cc8jThird Party Advisory
- https://datatracker.ietf.org/doc/html/rfc4343Third Party Advisory
- https://github.com/istio/istio/security/advisories/GHSA-7774-7vr3-cc8jThird Party Advisory
FAQ
What is CVE-2021-39155?
CVE-2021-39155 is a vulnerability with a CVSS score of 8.3 (HIGH). Istio is an open source platform for providing a uniform way to integrate microservices, manage traffic flow across microservices, enforce policies and aggregate telemetry data. According to [RFC 4343...
How severe is CVE-2021-39155?
CVE-2021-39155 has been rated HIGH with a CVSS base score of 8.3/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2021-39155?
Check the references section above for vendor advisories and patch information. Affected products include: Istio Istio.