{"id":"CVE-2026-40182","aliases":["GHSA-q834-8qmm-v933"],"url":"https://o3.security/vulnerability/CVE-2026-40182","summary":"OpenTelemetry dotnet: OTLP exporter reads unbounded HTTP response bodies","details":"### Summary\n\nWhen exporting telemetry to a back-end/collector over gRPC or HTTP using OpenTelemetry Protocol format (OTLP), if the request results in a unsuccessful request (i.e. HTTP 4xx or 5xx), the response is read into memory with no upper-bound on the number of bytes consumed.\n\nThis could cause memory exhaustion in the consuming application if the configured back-end/collector endpoint is attacker-controlled (or a network attacker can MitM the connection) and an extremely large body is returned by the response.\n\n### Details\n\nhttps://github.com/open-telemetry/opentelemetry-dotnet/pull/6564 introduced a change to read the response body when a non-200 HTTP status code is received when exporting telemetry to aid debugging by operators so that the error response is included in the logs emitted by the exporter for both [gRPC](https://github.com/open-telemetry/opentelemetry-dotnet/blob/640cf63628567b76b348b26988920dbc0b5c1662/src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/ExportClient/OtlpGrpcExportClient.cs#L123-L134) and [HTTP/protobuf](https://github.com/open-telemetry/opentelemetry-dotnet/blob/640cf63628567b76b348b26988920dbc0b5c1662/src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/ExportClient/OtlpHttpExportClient.cs#L36-L41).\n\nAn unintended consequence of this change is that the response body is [fully read into memory when received with no upper-bound](https://github.com/open-telemetry/opentelemetry-dotnet/blob/640cf63628567b76b348b26988920dbc0b5c1662/src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/ExportClient/OtlpExportClient.cs#L68-L89).\n\nThis vulnerability was surfaced during the investigation of GHSA-w8rr-5gcm-pp58.\n\n### Impact\n\nIf an application using the OTLP exporter is configured to use a back-end/collector endpoint that is attacker-controlled (or a network attacker can MitM the connection) and an extremely large body is returned by the response the application could have its memory exhausted and create a denial-of-service condition.\n\n### Mitigation\n\nThe 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.\n\n### Workarounds\n\nNone known.\n\n### Remediation\n\n[#7017](https://github.com/open-telemetry/opentelemetry-dotnet/pull/7017) updates the OTLP exporter for both gRPC and HTTP to:\n\n- Limit the number of bytes read from the response body in an error condition to 4MiB (see https://github.com/open-telemetry/opentelemetry-proto/pull/781);\n- Only attempt to read the response body if OpenTelemetry error logging is enabled.","published":"2026-04-23T17:51:34.961Z","modified":"2026-08-29T11:45:52.279917991Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"},"epss":{"score":0.00304,"percentile":0.22496,"asOf":"2026-08-24"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"NuGet","name":"OpenTelemetry.Exporter.OpenTelemetryProtocol","fixedVersion":"1.15.2"}],"fix":{"url":"https://github.com/open-telemetry/opentelemetry-dotnet/pull/6564","label":"open-telemetry/opentelemetry-dotnet#6564"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/40xxx/CVE-2026-40182.json"},{"type":"ADVISORY","url":"https://github.com/open-telemetry/opentelemetry-dotnet/security/advisories/GHSA-q834-8qmm-v933"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-40182"},{"type":"FIX","url":"https://github.com/open-telemetry/opentelemetry-dotnet/pull/6564"},{"type":"FIX","url":"https://github.com/open-telemetry/opentelemetry-dotnet/pull/7017"},{"type":"FIX","url":"https://github.com/open-telemetry/opentelemetry-proto/pull/781"},{"type":"PACKAGE","url":"https://github.com/open-telemetry/opentelemetry-dotnet"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-29T11:45:52.279917991Z"}}