gRPC — CWE-407 Disclosure Brief

2026-03-27 · Patch available — awaiting upstream merge

Finding

One O(n²) defect in gRPC's channelz property grid. GetIndex() in src/core/channelz/property_list.cc:28-36 uses std::find on std::vector<std::string> for column and row name lookup in PropertyGrid/PropertyTable, causing O(C²) + O(R²) overhead at high RPC rates. Patch ready for upstream review.

The Defects

grpc-0001 (PATCHED — HIGH): src/core/channelz/property_list.cc:28–36

// GetIndex() — per column/row name lookup:
size_t GetIndex(const std::vector<std::string>& names,
                const std::string& name) {
    auto it = std::find(names.begin(), names.end(), name);
    // O(C) scan per column lookup; O(R) per row lookup
    if (it == names.end()) { names.push_back(name); it = names.end() - 1; }
    return std::distance(names.begin(), it);
}
// At 1000 RPC/s × 50 metrics: O(C²) + O(R²) = 2.5M scans/sec

std::find O(C) scan per column name and O(R) scan per row name. At 1000 RPC/s with 50 metrics: 2.5M scans/sec. Measured ratio: 25×.

Complexity Proof

For C=25 columns, R=25 rows per channelz update at 1000 RPC/s:

Per update: O(C²) + O(R²) = 1,250 comparisons
Fixed: absl::flat_hash_map<std::string, size_t> shadow → O(C + R) per update
25× measured ratio.

Impact

All gRPC deployments using channelz — the gRPC observability and debugging interface. Channelz is enabled by default and provides metrics on channels, subchannels, and servers. High-throughput gRPC services (microservices, service meshes) calling channelz at high RPC rates hit O(C²) + O(R²) per metric update. gRPC is used in virtually all cloud-native and microservice architectures; it powers internal service communication at major technology companies.

The Fix

Add absl::flat_hash_map<std::string, size_t> shadow alongside the ordered vector:

// Before
size_t GetIndex(std::vector<std::string>& names, const std::string& name) {
    auto it = std::find(names.begin(), names.end(), name);  // O(n)
    ...
}

// After
// CWE-407 fix: absl::flat_hash_map shadow for O(1) index lookup alongside ordered vector.
size_t GetIndex(std::vector<std::string>& names,
                absl::flat_hash_map<std::string, size_t>& index,
                const std::string& name) {
    auto it = index.find(name);
    if (it == index.end()) {
        index[name] = names.size();
        names.push_back(name);
        return names.size() - 1;
    }
    return it->second;
}

Patch

defects/grpc/patch/grpc-0001-property-list-hashmap.patch

What We Ask

Confirm receipt and assign a GitHub Security Advisory or issue reference.
Validate the patch against your channelz and property grid test suite.
Assess CVE eligibility — 2.5M scans/sec at 1000 RPC/s with 50 metrics.
Coordinate a disclosure date — we are targeting 90 days from first contact.

Contact: see cover email. This brief is confidential until coordinated disclosure.

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