GHSA-MR8R-92FQ-PJ8P

Vulnerability from github – Published: 2026-04-23 21:40 – Updated: 2026-04-23 21:40
VLAI?
Summary
OpenTelemetry dotnet: Unbounded `grpc-status-details-bin` parsing in OTLP/gRPC retry handling
Details

Summary

When exporting telemetry over gRPC using the OpenTelemetry Protocol (OTLP), the exporter may parse a server-provided grpc-status-details-bin trailer during retry handling. Prior to the fix, a malformed trailer could encode an extremely large length-delimited protobuf field which was used directly for allocation, allowing excessive memory allocation and potential denial of service (DoS).

Details

5980 introduced a retry path that parses grpc-status-details-bin to extract gRPC retry delay information for retryable responses.

On that path:

  • OtlpGrpcExportClient captures grpc-status-details-bin from retryable status responses (ResourceExhausted / Unavailable).
  • OtlpRetry invokes GrpcStatusDeserializer.TryGetGrpcRetryDelay using this untrusted trailer value.
  • GrpcStatusDeserializer.DecodeBytes decoded a protobuf varint length and allocated new byte[length] without validating the bounds against the remaining payload size.

A malicious or compromised collector (or a MitM in weakly-protected deployments) could return a crafted grpc-status-details-bin payload that forces oversized allocation and memory exhaustion in the instrumented process.

Impact

If an OTLP/gRPC endpoint is attacker-controlled (or traffic is intercepted), a crafted retryable response can trigger large allocations during trailer parsing, which may exhaust memory and cause process instability/crash (availability impact / DoS).

Mitigation

The application's configured back-end/collector endpoint needs to behave maliciously. If the collector/back-end is a well-behaved implementation response bodies should not be excessively large if a request error occurs.

Workarounds

None known.

Remediation

#7064 updates GrpcStatusDeserializer to validate decoded length-delimited field sizes before allocation by ensuring the requested length is sane and does not exceed the remaining payload.

This causes malformed or truncated grpc-status-details-bin payloads to fail safely instead of attempting unbounded allocation.

Severity ?
5.3 (Medium)
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
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{
  "affected": [
    {
      "package": {
        "ecosystem": "NuGet",
        "name": "OpenTelemetry.Exporter.OpenTelemetryProtocol"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.13.1"
            },
            {
              "fixed": "1.15.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-40891"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-789"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-23T21:40:29Z",
    "nvd_published_at": "2026-04-23T18:16:28Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nWhen exporting telemetry over gRPC using the OpenTelemetry Protocol (OTLP), the exporter may parse a server-provided `grpc-status-details-bin` trailer during retry handling. Prior to the fix, a malformed trailer could encode an extremely large length-delimited protobuf field which was used directly for allocation, allowing excessive memory allocation and potential denial of service (DoS).\n\n### Details\n\n#5980 introduced a retry path that parses `grpc-status-details-bin` to extract gRPC retry delay information for retryable responses.\n\nOn that path:\n\n- `OtlpGrpcExportClient` captures `grpc-status-details-bin` from retryable status responses (`ResourceExhausted` / `Unavailable`).\n- `OtlpRetry` invokes `GrpcStatusDeserializer.TryGetGrpcRetryDelay` using this untrusted trailer value.\n- `GrpcStatusDeserializer.DecodeBytes` decoded a protobuf varint length and allocated `new byte[length]` without validating the bounds against the remaining payload size.\n\nA malicious or compromised collector (or a MitM in weakly-protected deployments) could return a crafted `grpc-status-details-bin` payload that forces oversized allocation and memory exhaustion in the instrumented process.\n\n### Impact\n\nIf an OTLP/gRPC endpoint is attacker-controlled (or traffic is intercepted), a crafted retryable response can trigger large allocations during trailer parsing, which may exhaust memory and cause process instability/crash (availability impact / DoS).\n\n### Mitigation\n\nThe application\u0027s configured back-end/collector endpoint needs to behave maliciously. If the collector/back-end is a well-behaved implementation response bodies should not be excessively large if a request error occurs.\n\n### Workarounds\n\nNone known.\n\n### Remediation\n\n[#7064](https://github.com/open-telemetry/opentelemetry-dotnet/pull/7064) updates `GrpcStatusDeserializer` to validate decoded length-delimited field sizes before allocation by ensuring the requested length is sane and does not exceed the remaining payload.\n\nThis causes malformed or truncated `grpc-status-details-bin` payloads to fail safely instead of attempting unbounded allocation.",
  "id": "GHSA-mr8r-92fq-pj8p",
  "modified": "2026-04-23T21:40:29Z",
  "published": "2026-04-23T21:40:29Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/open-telemetry/opentelemetry-dotnet/security/advisories/GHSA-mr8r-92fq-pj8p"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-40891"
    },
    {
      "type": "WEB",
      "url": "https://github.com/open-telemetry/opentelemetry-dotnet/pull/5980"
    },
    {
      "type": "WEB",
      "url": "https://github.com/open-telemetry/opentelemetry-dotnet/pull/7064"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/open-telemetry/opentelemetry-dotnet"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "OpenTelemetry dotnet: Unbounded `grpc-status-details-bin` parsing in OTLP/gRPC retry handling"
}


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