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VulnerabilityPublished

CVE-2026-42191: open-telemetry opentelemetry-dotnet · Creation of Temporary File in Directory with Insecure Permissions

Affects open-telemetry opentelemetry-dotnetSource CVE Database V5

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Not known to be exploited · CVSS 6.5 Medium : upgrade to 1.15.3 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
6.5Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 1% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 1.15.3
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 12 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade opentelemetry-dotnet and opentelemetry.exporter.opentelemetryprotocol to 1.15.3.

Affected software

ProductAffectedFixed in
open-telemetryopentelemetry-dotnetAffected
  • >=1.8.0 <1.15.3
Fixed in
  • 1.15.3
NuGetopentelemetry.exporter.opentelemetryprotocolpkg:nuget/opentelemetry.exporter.opentelemetryprotocolOther threatsAffected
  • >=1.8.0 <1.15.3
Fixed in
  • 1.15.3

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade opentelemetry-dotnet to version 1.15.3 or later, where this vulnerability is fixed by avoiding insecure use of the shared temporary directory for blob files. Until upgraded, consider configuring a secure, dedicated directory for OTEL_DOTNET_EXPERIMENTAL_OTLP_DISK_RETRY_DIRECTORY_PATH to restrict access. Patch status is not explicitly stated in the vendor advisory, but the fix is included in version 1.15.3.

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.

References

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