CVE-2026-126360 (CVSS 5.3)

Description

OpenTelemetry Python provides the Python API and SDK for OpenTelemetry. Prior to 1.45.2, TraceContextTextMapPropagator.extract() in opentelemetry-api can perform quadratic-time regular-expression backtracking on a malformed traceparent value containing a trace-context prefix, a long whitespace sequence, and an embedded newline. Exploitation requires an attacker-controlled carrier that preserves embedded newlines and permits a sufficiently large value, because conforming HTTP header values cannot contain embedded newlines. JSON-based carriers, including applicable MCP request metadata integrations, can preserve the required newline depending on the SDK, instrumentation, and message-size limits. Parsing on an asynchronous server's event-loop thread can consume excessive CPU and delay unrelated requests, while the advisory does not establish disclosure, modification, or code execution. This issue is fixed in version 1.45.2.

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CVSS v3.1 Score

5.3

MEDIUM

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

Weakness Type (CWE)

CWE-1333 CWE-1333

References

Other References

https://github.com/open-telemetry/opentelemetry-python/commit/78123a2755c907c602e02352aebed4be86aa5350 https://github.com/open-telemetry/opentelemetry-python/commit/faa72dae511ae64a7bf8ca63eff9ad4387d0b939 https://github.com/open-telemetry/opentelemetry-python/pull/5818 https://github.com/open-telemetry/opentelemetry-python/pull/5856 https://github.com/open-telemetry/opentelemetry-python/releases/tag/v1.45.2 https://github.com/open-telemetry/opentelemetry-python/security/advisories/GHSA-mf5v-w3w3-f6cg

Frequently Asked Questions

What is CVE-2026-126360? +

OpenTelemetry Python provides the Python API and SDK for OpenTelemetry. Prior to 1.45.2, TraceContextTextMapPropagator.extract() in opentelemetry-api can perform quadratic-time regular-expression backtracking on a malformed traceparent value containing a trace-context prefix, a long whitespace sequence, and an embedded newline. Exploitation requires an attacker-controlled carrier that preserves embedded newlines and permits a sufficiently large value, because conforming HTTP header values cannot contain embedded newlines. JSON-based carriers, including applicable MCP request metadata integrations, can preserve the required newline depending on the SDK, instrumentation, and message-size limits. Parsing on an asynchronous server's event-loop thread can consume excessive CPU and delay unrelated requests, while the advisory does not establish disclosure, modification, or code execution. This issue is fixed in version 1.45.2. It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2026-126360? +

CVE-2026-126360 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

How do I check if I'm vulnerable to CVE-2026-126360? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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