OpenTelemetry.Exporter.OpenTelemetryProtocol: Disk retry default temp path enables local blob injection for OTLP Exporter

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

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.

Source published

12 May 2026 19:12:03 UTC

Source modified

13 May 2026 14:16:18 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 6.5 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L

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.

Source published

May 12, 2026, 7:12:03 PM (timezone not stated)

Source modified

May 13, 2026, 2:16:18 PM (timezone not stated)

Observed here

7 Nov 2026 09:32:28 UTC

Source terms

ENISA EUVD · source terms and attribution apply

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 6.5 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L

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.

Source published

12 May 2026 20:16:41 UTC

Source modified

26 Oct 2026 18:10:00 UTC

Observed here

27 Oct 2026 11:12:01 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 6.5 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L

CVSS 3.1 · [email protected] · Primary · 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

### Summary 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 exposed three attack surfaces: - **Blob injection (integrity):** an attacker could write crafted `*.blob` files into the predictable path; the exporter picks them up on the next retry cycle and forwards them to the configured OTLP endpoint under the application's identity. - **Telemetry disclosure (confidentiality):** an attacker reads `*.blob` files written by the application between export failures, recovering encoded telemetry payloads (spans, metric data points, log records). - **Resource exhaustion (availability):** an attacker deposits numerous or oversized blob files, degrading retry-loop performance or consuming disk space. ### Details #### Preconditions 1. `OTEL_DOTNET_EXPERIMENTAL_OTLP_RETRY` is set to `disk`. 2. `OTEL_DOTNET_EXPERIMENTAL_OTLP_DISK_RETRY_DIRECTORY_PATH` is not set, causing the exporter to resolve the blob storage root using the `System.IO.Path.GetTempPath()` API. 3. A local attacker has read or write access to the process' temporary directory (e.g., `/tmp` on Linux, or `%TEMP%` on a multi-user Windows installation). #### Exploit path 1. A target application starts with `OTEL_DOTNET_EXPERIMENTAL_OTLP_RETRY=disk` and no explicit blob directory. The exporter resolves the storage root to `Path.GetTempPath()`, producing paths such as `%TEMP%\traces`, `%TEMP%\metrics`, and `%TEMP%\logs` (or `/tmp/traces` etc. on Linux). 2. **Injection scenario:** before or during the application's retry window, an attacker writes crafted `*.blob` files into one of those signal subdirectories. On the next retry interval (by default every 60 seconds), [`OtlpExporterPersistentStorageTransmissionHandler`](https://github.com/open-telemetry/opentelemetry-dotnet/blob/c724f4bd6fd88e9a599af1668bf7af9487155b62/src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/Transmission/OtlpExporterPersistentStorageTransmissionHandler.cs) scans the directory, loads the attacker-supplied blobs, and forwards them to the configured OTLP endpoint using the application's identity and transport credentials. 3. **Disclosure scenario:** the attacker reads `*.blob` files that the application wrote after a transient export failure, recovering the full serialized telemetry payloads (spans, metric data points, or log records in Protobuf encoding). 5. **DoS scenario:** the attacker deposits a large number of oversized blob files in the temporary subdirectories, causing the retry loop to consume excess CPU/IO processing them, potentially exhausting available disk space. ### Mitigations If an immediate upgrade to a patched version is not possible: 1. Avoid enabling disk retry in shared environments. 2. Configure a dedicated directory with strict ACL/ownership and least privilege. 3. Ensure the directory is not shared across tenants/users. 4. Monitor for unexpected `*.blob` files or abnormal retry backlog growth. ### Resources - [#7106](https://github.com/open-telemetry/opentelemetry-dotnet/pull/7106)

Source published

30 Apr 2026 18:34:30 UTC

Source modified

10 Sep 2026 03:50:43 UTC

Observed here

23 Oct 2026 16:01:25 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L

Publisher rating · MODERATE