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EUVD-2026-317993

fkie_cve-2026-42191

OpenTelemetry.Exporter.OpenTelemetryProtocol is the OTLP (OpenTelemetry Protocol) exporter implementation. From 1.8.0 to 1.15.2, the OTLP disk retry feature in OpenTelemetry.Exporter.OpenTelemetryProtocol silently fell back to Path.GetTempPath() when OTEL_DOTNET_EXPERIMENTAL_OTLP_RETRY=disk was set but OTEL_DOTNET_EXPERIMENTAL_OTLP_DISK_RETRY_DIRECTORY_PATH was not configured. The exporter stored and loaded *.blob files under fixed, signal-named subdirectories (traces, metrics, logs) beneath that shared temporary root path. On multi-user systems where the temporary directory is accessible to other local accounts, this allows an attacker to write crafted *.blob files, read *.blob files written by the application between export failures, or deposit numerous or oversized blob files, degrading retry-loop performance or consuming disk space. This vulnerability is fixed in 1.15.3.

GHSA-4625-4j76-fww9 — OpenTelemetry's disk retry default temp path enables local blob injection via OTLP Exporter

Affected: NuGet: OpenTelemetry.Exporter.OpenTelemetryProtocol

### Summary

The OTLP disk retry feature in `OpenTelemetry.Exporter.OpenTelemetryProtocol` silently fell back to `Path.GetTempPath()` when `OTEL_DOTNET_EXPERIMENTAL_OTLP_RETRY=disk` was set but `OTEL_DOTNET_EXPERIMENTAL_OTLP_DISK_RETRY_DIRECTORY_PATH` was not configured.

The exporter stored and loaded `*.blob` files under fixed, signal-named subdirectories (`traces`, `metrics`, `logs`) beneath that shared temporary root path.

On multi-user systems where the temporary directory is accessible to other local accounts, this exposed three attack surfaces:

- **Blob injection (integrity):** an attacker could write crafted `*.blob` files into the predictable path; the exporter picks them up on the next retry cycle and forwards them to the configured OTLP endpoint under the application's identity. - **Telemetry disclosure (confidentiality):** an attacker reads `*.blob` files written by the application between export failures, recovering encoded telemetry payloads (spans, metric data points, log records). - **Resource exhaustion (availability):** an attacker deposits numerous or oversized blob files, degrading retry-loop performance or consuming disk space.

### Details

#### Preconditions

1. `OTEL_DOTNET_EXPERIMENTAL_OTLP_RETRY` is set to `disk`. 2. `OTEL_DOTNET_EXPERIMENTAL_OTLP_DISK_RETRY_DIRECTORY_PATH` is not set, causing the exporter to resolve the blob storage root using the `System.IO.Path.GetTempPath()` API. 3. A local attacker has read or write access to the process' tem…