An issue was discovered in Istio 1.3 through 1.3.6. Under certain circumstances, it is possible to bypass a specifically configured Mixer policy. Istio-proxy accepts the x-istio-attributes header at ingress that can be used to affect policy decisions when Mixer policy selectively applies to a source equal to ingress. To exploit this vulnerability, someone has to encode a source.uid in this header. This feature is disabled by default in Istio 1.3 and 1.4.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-8843
• https://github.com/istio/istio/commits/master
• https://istio.io/news/security/
• https://istio.io/news/security/istio-security-2020-002/