opentelemetry-dotnet: Creation of Temporary File in Directory with Insecure Permissions
CVE-2026-42191 is a high-severity creation of temporary file in directory with insecure permissions vulnerability in opentelemetry-dotnet from Open-telemetry, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. Affected opentelemetry-dotnet versions: >= 1.8.0, < 1.15.3. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.11% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Opentelemetry.exporter.opentelemetryprotocol to 1.15.3 or a later version.
- Read the advisory on github.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Open-telemetry | opentelemetry-dotnet | >= 1.8.0, < 1.15.3 | Not stated |
| Opentelemetry | Opentelemetry.exporter.opentelemetryprotocol | 1.8.0 up to, but not including, 1.15.3 | 1.15.3 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 6.5 | Medium | CNA (github.com) |
| CVSS 3.1 | 7.8 | High | NVD |
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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Creation of Temporary File in Directory with Insecure Permissions
The product creates a temporary file in a directory whose permissions allow unintended actors to determine the file's existence or otherwise access that file.
How developers prevent this class of flaw
- Many contemporary languages have functions which properly handle this condition. Older C temp file functions are especially susceptible.
- Try to store sensitive tempfiles in a directory which is not world readable -- i.e., per-user directories.
- Avoid using vulnerable temp file functions.
More Creation of Temporary File in Directory with Insecure Permissions vulnerabilities (CWE-379)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Patches and release notes
- github.com/open-telemetry/opentelemetry-dotnet/pull/7106Issue Tracking
Other vulnerabilities in opentelemetry-dotnet
- 7.5 High severity
Recent Creation of Temporary File in Directory with Insecure Permissions vulnerabilities
- 7.0 High severity
- 7.3 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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