CVE-2020-11767

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in, but needs a user to act. Limited direct impact.

Exploit odds

1.8% chance of exploitation in the next 30 days (EPSS).

Fix

No patch or advisory is linked yet. Look at mitigations or restrict exposure.

Timeline

1. 2020-04-15 02:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 02:50 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.8% in the next 30 days (EPSS).
• Severity: 3.1 LOW (CVSS).
• Fix: none linked yet, which raises it.

Details

Published

2020-04-15 02:15 UTC

Last modified

2026-06-17 02:50 UTC

Exploit probability

1.8% · EPSS, next 30 days

Record status

Modified

Affected

• Envoyproxy Envoy ≤ 1.14.1
• Istio ≤ 1.5.1

Attack profile CVSS 3.1 · 3.1

Attack vector

Network

Complexity

High

Privileges needed

None

User interaction

Required

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2020-11767.md and follow it. Check whether this project is affected by CVE-2020-11767. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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