CVE-2020-11767: Istio through 1.5.1 and Envoy through 1.14.1 have a data-leak issue. If there is a TCP connection (negotiated with SNI over HTTPS) to *.example.com, a...

Description

Istio through 1.5.1 and Envoy through 1.14.1 have a data-leak issue. If there is a TCP connection (negotiated with SNI over HTTPS) to *.example.com, a request for a domain concurrently configured explicitly (e.g., abc.example.com) is sent to the server(s) listening behind *.example.com. The outcome should instead be 421 Misdirected Request. Imagine a shared caching forward proxy re-using an HTTP/2 connection for a large subnet with many users. If a victim is interacting with abc.example.com, and a server (for abc.example.com) recycles the TCP connection to the forward proxy, the victim's browser may suddenly start sending sensitive data to a *.example.com server. This occurs because the forward proxy between the victim and the origin server reuses connections (which obeys the specification), but neither Istio nor Envoy corrects this by sending a 421 error. Similarly, this behavior voids the security model browsers have put in place between domains.

Metrics

CVSS 3.1

3.1/10

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N

EPSS Probability

1.77%

75.4th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Envoyproxy	Envoy	<= 1.14.1
Istio	Istio	<= 1.5.1

References

https://bugs.chromium.org/p/chromium/issues/detail?id=954160#c5Issue Tracking, Third Party Advisory
https://github.com/envoyproxy/envoy/issues/6767Third Party Advisory
https://github.com/istio/istio/issues/13589Exploit, Third Party Advisory
https://github.com/istio/istio/issues/9429Third Party Advisory
https://bugs.chromium.org/p/chromium/issues/detail?id=954160#c5Issue Tracking, Third Party Advisory
https://github.com/envoyproxy/envoy/issues/6767Third Party Advisory
https://github.com/istio/istio/issues/13589Exploit, Third Party Advisory
https://github.com/istio/istio/issues/9429Third Party Advisory

Timeline

Published: Apr 15, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-11767?

Istio through 1.5.1 and Envoy through 1.14.1 have a data-leak issue. If there is a TCP connection (negotiated with SNI over HTTPS) to *.example.com, a request for a domain concurrently configured explicitly (e.g., abc.example.com) is sent to the server(s) listening behind *.example.com. The outcome should instead be 421 Misdirected Request. Imagine a shared caching forward proxy re-using an HTTP/2 connection for a large subnet with many users. If a victim is interacting with abc.example.com, and a server (for abc.example.com) recycles the TCP connection to the forward proxy, the victim's browser may suddenly start sending sensitive data to a *.example.com server. This occurs because the forward proxy between the victim and the origin server reuses connections (which obeys the specification), but neither Istio nor Envoy corrects this by sending a 421 error. Similarly, this behavior voids the security model browsers have put in place between domains.

How severe is CVE-2020-11767?

CVE-2020-11767 has a CVSS score of 3.1/10 (LOW severity). The EPSS model estimates a 1.77% probability of exploitation in the next 30 days.

How do I fix CVE-2020-11767?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.