CVE-2026-44213

The OpenTelemetry.Exporter.Instana NuGet package does not validate HTTPS/TLS certificates are valid when sending telemetry to a configured Instana back-end when a proxy is configured using the INSTANA_ENDPOINT_PROXY environment variable.

If a network attacker can Man-in-the-Middle (MitM) the proxy connection, all OpenTelemetry telemetry data and the Instana API key are exposed to the attacker.

Details

The Transport.ConfigureBackendClient() method creates an HttpClient instance that completely disables TLS server certificate validation if the INSTANA_ENDPOINT_PROXY is configured with a valid proxy URL with no ability to re-enable it.

Mitigation

The proxy configured by the INSTANA_ENDPOINT_PROXY environment variable must be malicious or be possible to be subject to a MitM attack.

Workarounds

Do not configure the INSTANA_ENDPOINT_PROXY environment variable.

Resources

• PR #4153

If the configured proxy is attacker-controlled (or a network attacker MitM the connection), or if it is possible for the process' configuration to be changed to add an attacker-provided value for INSTANA_ENDPOINT_PROXY then all Instana telemetry could be read by an unauthorized party and the service's Instana API key compromised, potentially before being forwarded to Instana presenting no noticeable loss of telemetry data without a valid TLS server certificate being presented to the client that matches the expected hostname or IP address.

CVE-2026-44213 has a CVSS score of 6.5 (Medium). The vector is network-reachable, high privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.1.0); upgrading removes the vulnerable code path.

Kodem intelligence

#4153 refactors HttpClient creation so that TLS certificate validation is no longer disabled by default when using a proxy.

In environments where this capability is required, for example for local development, the previous behaviour can be restored using the `` option:

builder.AddInstanaExporter((options) =>
{
    options.HttpClientFactory = () =>
    {
        var handler = new HttpClientHandler()
        {
#if NET
            ServerCertificateCustomValidationCallback = HttpClientHandler.DangerousAcceptAnyServerCertificateValidator,
#else
            ServerCertificateCustomValidationCallback = static (_, _, _, _) => true,
#endif
        };
        return new HttpClient(handler, disposeHandler: true);
    };
});

1. What is CVE-2026-44213? CVE-2026-44213 is a medium-severity security vulnerability in OpenTelemetry.Exporter.Instana (nuget), affecting versions <= 1.0.7. It is fixed in 1.1.0.
2. How severe is CVE-2026-44213? CVE-2026-44213 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of OpenTelemetry.Exporter.Instana are affected by CVE-2026-44213? OpenTelemetry.Exporter.Instana (nuget) versions <= 1.0.7 is affected.
4. Is there a fix for CVE-2026-44213? Yes. CVE-2026-44213 is fixed in 1.1.0. Upgrade to this version or later.
5. Is CVE-2026-44213 exploitable, and should I be worried? Whether CVE-2026-44213 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-44213 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-44213? Upgrade OpenTelemetry.Exporter.Instana to 1.1.0 or later.