CVE-2021-32780
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedEnvoy 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceEnvoy proxy contains a state machine flaw where receiving a GOAWAY frame (transitioning to CLOSED state) followed by a SETTINGS frame with SETTINGS_MAX_CONCURRENT_STREAMS=0 in the same I/O event causes an invalid state transition from CLOSED to DRAINING, resulting in abnormal process termination and denial of service.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 1.18.0, < 1.18.4= 1.19.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Envoy process and binary versionRun 'envoy --version' on the running binary, or inspect the container image tag if Envoy runs in a container, or check the process executable path via 'ps aux | grep envoy'Affected if The version is 1.18.0, 1.18.1, 1.18.2, 1.18.3, or 1.19.0
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Confirm HTTP/2 upstream connections are configuredInspect Envoy configuration (static config file, dynamic resources, or 'envoyadmin <address> server_info' output) and look for cluster definitions with 'http2_protocol_options' set, or verify default HTTP/2 behavior for upstream connectionsAffected if Any upstream cluster uses HTTP/2 (h2) protocol, which is the default for many upstream connections in Envoy
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Check for exposure to untrusted upstream serversReview Envoy listener and cluster configuration to determine if upstream connections originate from servers outside your trust boundary (external APIs, third-party services, or untrusted network segments)Affected if Envoy establishes upstream HTTP/2 connections to servers you do not fully control
You are affected if you run Envoy version 1.18.0 through 1.18.3 or exactly 1.19.0, have HTTP/2 enabled for upstream connections, and connect to upstream servers that could send the triggering frame sequence
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped1.18.4
Upgrade Envoy to version 1.19.1 or 1.18.4 which contain fixes to stop processing pending H/2 frames after connection transition to CLOSED state; alternatively, restrict or validate upstream server connections to trusted sources.
1.18.4 for 1.18.x branches; 1.19.1 for 1.19.0
- Identify current Envoy version using envoy --version
- If running Envoy 1.18.x (>=1.18.0, <1.18.4): upgrade to Envoy 1.18.4
- If running Envoy 1.19.0: upgrade to Envoy 1.19.1
- Verify the upgrade was successful by checking envoy --version
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-32780 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-32780 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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