CVE-2021-36153
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 · uneditedMismanaged state in GRPCWebToHTTP2ServerCodec.swift in gRPC Swift 1.1.0 and 1.1.1 allows remote attackers to deny service by sending malformed requests.
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 · moderate confidenceMismanaged state in GRPCWebToHTTP2ServerCodec.swift in gRPC Swift versions 1.1.0 and 1.1.1 allows remote attackers to cause denial of service by sending malformed HTTP/2 requests through the gRPC-web gateway, triggering an unhandled state error.
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= 1.1.0= 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 installed gRPC Swift versionCheck your project's dependency manifest (Package.swift, Podfile, or similar) for the grpc-swift package version, or run 'swift package show dependencies' if using Swift Package ManagerAffected if The installed version is 1.1.0 or 1.1.1
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Locate GRPCWebToHTTP2ServerCodec.swift in your deploymentSearch for this file in your gRPC Swift source code or compiled binary - it is part of the grpc-swift library and handles the gRPC-web to HTTP/2 protocol translationAffected if This codec is present in your deployed gRPC Swift library version 1.1.0 or 1.1.1
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Verify gRPC-web gateway is enabledInspect your server configuration or startup code for gRPC-web endpoint exposure. Look for gRPC-web middleware, gateway proxy configuration, or HTTP/1.1-to-HTTP/2 bridging setupAffected if Your service exposes a gRPC-web gateway endpoint that routes requests through GRPCWebToHTTP2ServerCodec
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Check HTTP/2 request handlingReview network logs or enable debug logging for HTTP/2 traffic to observe how malformed requests are processed by your gRPC-web gatewayAffected if The server processes HTTP/2 requests from gRPC-web clients without strict validation
You are affected if gRPC Swift version 1.1.0 or 1.1.1 is deployed AND the gRPC-web gateway component (GRPCWebToHTTP2ServerCodec) is in use, allowing external HTTP/2 requests to reach the vulnerable code path.
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 gRPC Swift to version 1.1.2 or later where the state management in GRPCWebToHTTP2ServerCodec has been fixed; if immediate patching is not feasible, implement request validation and rate limiting at a proxy or load balancer to filter malformed requests.
- Consultation2.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,328.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-36153 — 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-2021-36153 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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