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.

Published · last modified .

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.

EPSS exploit prediction

EPSS: 0.001 (3.6th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 4th percentile — 3.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-42191: held from 0.001 to 0.001.

EPSS over last 30 days · oldest: 0.001 · newest: 0.001 · change: +0.000

Affected products

Weakness classification (CWE)

References

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.