PYSEC-2026-3461

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PYSEC-2026-3461

Summary: dd-trace-py: Improper parsing of W3C baggage headers may lead to DoS

Details: ### Impact Datadog tracing libraries that implement W3C baggage propagation parse incoming baggage HTTP headers without enforcing item-count or byte-size limits on the extract path. The DD_TRACE_BAGGAGE_MAX_ITEMS (default 64) and DD_TRACE_BAGGAGE_MAX_BYTES (default 8192) limits were applied only to baggage injection, not extraction. A remote, unauthenticated attacker can send a request whose baggage header contains an arbitrarily large number of comma-separated key-value pairs (or a single very large value). The tracer allocates a hash-map entry for each pair on every request, causing unbounded CPU and memory consumption and enabling a remote Denial of Service against any HTTP service that has the baggage propagation style enabled. The baggage propagation style is enabled by default in most affected tracers, so any internet-facing service that has been instrumented with an affected tracer version is exposed unless the propagation style has been explicitly narrowed. ### Patches This is resolved in version 4.8.2 and later of the `dd-trace-py` library ### Workarounds If users cannot upgrade immediately: 1. Disable `baggage` extraction by removing `baggage` from `DD_TRACE_PROPAGATION_STYLE` (or `DD_TRACE_PROPAGATION_STYLE_EXTRACT` if set independently). 2. Cap the maximum HTTP request header size at an upstream proxy or web server (for example, Apache `LimitRequestFieldSize`, Nginx `large_client_header_buffers`, Envoy `max_request_headers_kb`). ### Resources Related upstream advisories: [opentelemetry-go GHSA-mh2q-q3fh-2475](https://github.com/open-telemetry/opentelemetry-go/security/advisories/GHSA-mh2q-q3fh-2475) [opentelemetry-dotnet GHSA-g94r-2vxg-569j](https://github.com/open-telemetry/opentelemetry-dotnet/security/advisories/GHSA-g94r-2vxg-569j)

References: https://github.com/DataDog/dd-trace-py/security/advisories/GHSA-mw54-j2v2-42hr, https://github.com/DataDog/dd-trace-py, https://pypi.org/project/ddtrace, https://github.com/advisories/GHSA-mw54-j2v2-42hr, https://nvd.nist.gov/vuln/detail/CVE-2026-50271