CVE-2021-36154
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 · uneditedHTTP2ToRawGRPCServerCodec in gRPC Swift 1.1.1 and earlier allows remote attackers to deny service via the delivery of many small messages within a single HTTP/2 frame, leading to Uncontrolled Recursion and stack consumption.
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 confidenceThe HTTP2ToRawGRPCServerCodec in gRPC Swift versions 1.1.1 and earlier contains a denial-of-service vulnerability where processing many small messages within a single HTTP/2 frame triggers uncontrolled recursion, leading to stack consumption and service failure.
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= 1.0.0= 1.1.0= 1.1.1CVSS 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 if gRPC Swift is in useSearch your codebase or dependency manifests (Package.swift, Package.resolved, or similar) for references to grpc-swift or the package URL https://github.com/grpc/grpc-swiftAffected if gRPC Swift is present in your dependencies
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Determine the installed gRPC Swift versionCheck your dependency lock file (Package.resolved) or query the package manager: swift package show dependencies | grep grpc or swift package resolve --verbose 2>&1 | grep grpc-swiftAffected if The resolved version is 1.0.0, 1.1.0, or 1.1.1
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Verify usage of HTTP2ToRawGRPCServerCodecSearch your source code for imports of grpc or any custom ServerChannelHandler implementation that wraps HTTP2ToRawGRPCServerCodec (grep -r 'HTTP2ToRawGRPCServerCodec' or inspect your gRPC server initialization code)Affected if Your server code uses this codec to handle HTTP/2 to gRPC transcoding
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Check if the server accepts streaming or batched messagesReview your server method handlers and RPC configuration to determine if clients can send multiple messages within a single HTTP/2 DATA frame or stream multiple small messages rapidlyAffected if Your gRPC service processes streaming RPCs or handles high-frequency small messages from clients on HTTP/2 connections
You are affected if gRPC Swift versions 1.0.0, 1.1.0, or 1.1.1 are installed AND your server uses HTTP2ToRawGRPCServerCodec to handle HTTP/2 connections that can receive multiple messages per frame.
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.
From vendor dataUpgrade to gRPC Swift version 1.1.2 or later which contains the fix for this vulnerability; implement rate limiting on the server side as an additional defensive measure.
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-36154 — 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-2021-36154 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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