# 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.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L`)
- **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:** Yes
- **Published:** 12 May 2026
- **Updated:** 13 May 2026
- **Also known as:** GHSA-4625-4j76-fww9, MINI-54hj-79vx-69fg

## 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 (Creation of Temporary File in Directory with Insecure Permissions)

## 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 | Ecosystem | 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: Opentelemetry Opentelemetry.exporter.opentelemetryprotocol.

## How do I fix CVE-2026-42191?

Upgrade OpenTelemetry.Exporter.OpenTelemetryProtocol to 1.15.3 or later.

## Is CVE-2026-42191 being exploited?

There is no known exploitation of CVE-2026-42191 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42191 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-42191 in the wild and no public exploit code.

Affected packages and fixed versions:
- OpenTelemetry.Exporter.OpenTelemetryProtocol (NuGet): affected from 1.8.0; fixed in 1.15.3
- OpenTelemetry.Exporter.OpenTelemetryProtocol (NuGet): affected from 1.8.0; fixed in 1.15.3

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-42191/ (Markdown: https://insights.sbomify.com/CVE-2026-42191/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42191
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42191
- OSV: https://osv.dev/vulnerability/CVE-2026-42191

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42191/
Summaries are generated and may contain mistakes; the official description above is the record.