CVE-2026-107286

Pydantic AI is a Python agent framework for building applications and workflows with Generative AI. From 2.10.0 until 2.53.0, streamed requests made through ConcurrencyLimitedModel or limit_model_concurrency can retain shared concurrency slots because anyio.CapacityLimiter associates an acquired slot with the borrowing task while streaming cleanup can run in a different task. Early stream termination, cancellation, consumer exceptions, or complete stream_text() consumption with debounce_by=0.1 can therefore leave capacity occupied, eventually preventing later requests that share the long-lived limiter from proceeding and causing a denial of service. Agent-level max_concurrency and non-streaming model requests are not affected. This issue is fixed in version 2.53.0.

• CWE-772

• https://github.com/pydantic/pydantic-ai/commit/453f19feeb7ab1d789f9393b1723c6a73b3d77b2
• https://github.com/pydantic/pydantic-ai/pull/9478
• https://github.com/pydantic/pydantic-ai/releases/tag/v2.53.0
• https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-6fqq-452j-qhrp

Published

Oct 8, 2026

Last Modified

Oct 8, 2026

Status

Received

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