Vulnerability in Open-Telemetry Opentelemetry-Dotnet
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.
EPSS: 0.001 (1.3th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L.
Affected products
- Open-telemetry Opentelemetry-dotnet — versions >= 1.8.0, < 1.15.3
- Opentelemetry Opentelemetry.exporter.opentelemetryprotocol
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Mitigation, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC, Issue Tracking)
Frequently asked questions
- What is CVE-2026-42191?
- CVE-2026-42191 is a medium-severity vulnerability in Open-Telemetry Opentelemetry-Dotnet, classified under Creation of Temporary File in Directory with Insecure Permissions. CVSS score: 6.5/10. Published 2026-05-12.
- How severe is CVE-2026-42191?
- Medium severity. CVSS v3 base score is 6.5 out of 10.