CVE-2026-42191 OpenTelemetry's disk retry default temp path enables local blob injection via OTLP Exporter
Local attackers can inject or read telemetry data via shared temp files when disk retry is enabled without a custom directory.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-42191?
CVE-2026-42191 is a medium-severity path traversal vulnerability in open-telemetry opentelemetry-dotnet, published on 12 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Weakness: CWE-379
Which versions are affected by CVE-2026-42191?
2 open source packages ship an affected version, including OpenTelemetry.Exporter.OpenTelemetryProtocol. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
OpenTelemetry.Exporter.OpenTelemetryProtocol NuGet | From 1.8.0 | 1.15.3 |
OpenTelemetry.Exporter.OpenTelemetryProtocol NuGet | From 1.8.0 | 1.15.3 |
Products include Opentelemetry Opentelemetry.exporter.opentelemetryprotocol.
How do I fix CVE-2026-42191?
Upgrade OpenTelemetry.Exporter.OpenTelemetryProtocol to 1.15.3 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-42191 being exploited?
There is no known exploitation of CVE-2026-42191 in the wild and no public exploit code.
Sources
Also known as GHSA-4625-4j76-fww9, MINI-54hj-79vx-69fg.