# CVE-2026-42191

## Summary

- **CVE ID:** CVE-2026-42191
- **Severity:** MEDIUM
- **CVSS Score:** 6.5 (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L)
- **CWE:** CWE-379
- **Published:** May 12, 2026
- **Last Modified:** May 13, 2026

## Description

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.

## Affected Products

- open-telemetry — opentelemetry-dotnet (>= 1.8.0, < 1.15.3)

## References

- [CNA](https://github.com/open-telemetry/opentelemetry-dotnet/security/advisories/GHSA-4625-4j76-fww9)
- [CNA](https://github.com/open-telemetry/opentelemetry-dotnet/pull/7106)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.11%
- **EPSS Percentile:** 1.3

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._