# CVE-2026-126360: OpenTelemetry Python: Denial of service through quadratic-time traceparent parsing in opentelemetry-api

Status: published. Published: 2026-11-12. Updated: 2026-11-12.

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.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- open-telemetry / opentelemetry-python: < 1.45.2 (affected). Source: CNA: GitHub_M

## Severity and prioritization

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-1333

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/open-telemetry/opentelemetry-python/security/advisories/GHSA-mf5v-w3w3-f6cg (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/open-telemetry/opentelemetry-python/pull/5818 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/open-telemetry/opentelemetry-python/pull/5856 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/open-telemetry/opentelemetry-python/commit/78123a2755c907c602e02352aebed4be86aa5350 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/open-telemetry/opentelemetry-python/commit/faa72dae511ae64a7bf8ca63eff9ad4387d0b939 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/open-telemetry/opentelemetry-python/releases/tag/v1.45.2 (CNA: GitHub_M; x_refsource_MISC)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-126360; retrieved 2026-11-12; source updated 2026-11-12

Revision: 7bf58283dbfa83c712bd5eb0fc677920d42ecdac7d4e83a90ee7a8db0ee829db

Canonical: https://y2.dev/cve/CVE-2026-126360

## Agent and API access

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- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.