CVE-2021-32781
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 after Envoy sends a locally generated response it must stop further processing of request or response data. However when local response is generated due the internal buffer overflow while request or response is processed by the filter chain the operation may not be stopped completely and result in accessing a freed memory block. A specifically constructed request delivered by an untrusted downstream or upstream peer in the presence of extensions that modify and increase the size of request or response bodies resulting in a Denial of Service when using extensions that modify and increase the size of request or response bodies, such as decompressor filter. Envoy versions 1.19.1, 1.18.4, 1.17.4, 1.16.5 contain fixes to address incomplete termination of request processing after locally generated response. As a workaround disable Envoy's decompressor, json-transcoder or grpc-web extensions or proprietary extensions that modify and increase the size of request or response bodies, if feasible.
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 fails to properly terminate request/response processing after generating a local response due to buffer overflow conditions. When extensions that increase request/response body size (decompressor, json-transcoder, grpc-web) are used, a specially crafted request can cause Envoy to access freed memory, resulting in 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>= 1.16.0, < 1.16.5>= 1.17.0, < 1.17.4>= 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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Check Envoy versionRun `envoy --version` or examine the binary metadata to identify the installed Envoy versionAffected if Version is >=1.16.0 and <1.16.5, OR >=1.17.0 and <1.17.4, OR >=1.18.0 and <1.18.4, OR equals 1.19.0
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Inspect for decompressor filterSearch Envoy configuration (YAML/JSON) for `envoy.filters.http.decompressor` in the http_filters chainAffected if The decompressor filter is present and Envoy version is in a vulnerable range
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Inspect for json-transcoder filterSearch Envoy configuration for `envoy.filters.http.json_transcoder` in the http_filters chainAffected if The json-transcoder filter is present and Envoy version is in a vulnerable range
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Inspect for grpc-web filterSearch Envoy configuration for `envoy.filters.http.grpc_web` in the http_filters chainAffected if The grpc-web filter is present and Envoy version is in a vulnerable range
You are affected if your Envoy version falls within the vulnerable ranges AND at least one of these extensions (decompressor, json-transcoder, or grpc-web) is enabled in your configuration.
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 · scoped1.16.51.17.41.18.4
Upgrade Envoy to versions 1.19.1, 1.18.4, 1.17.4, or 1.16.5 and later, or disable decompressor, json-transcoder, grpc-web, and similar body-modifying extensions as a workaround.
1.16.5, 1.17.4, 1.18.4, or 1.19.1 (depending on current major.minor version)
- 1. Identify current Envoy version by checking envoy --version or the deployed image tag
- 2. Based on current version, plan upgrade target: if 1.16.x upgrade to 1.16.5; if 1.17.x upgrade to 1.17.4; if 1.18.x upgrade to 1.18.4; if 1.19.0 upgrade to 1.19.1 or later
- 3. If upgrading major/minor version, review Envoy release notes for breaking changes between versions
- 4. Test the upgrade in a staging environment before production deployment
- 5. Deploy the new Envoy version
- 6. Alternatively, if upgrade is not immediately feasible, disable problematic extensions (decompressor, json-transcoder, grpc-web) in the Envoy configuration as a temporary mitigation
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation3.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-32781 — 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-2021-32781 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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