Pydantic AI: Concurrency-limited models can keep their slot when a streamed request ends early

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-107286
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-08 15:17:40 UTC
Updated2026-10-08 18:17:16 UTC
DescriptionPydantic 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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

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

Problem Types: CWE-772 | CWE-772 CWE-772: Missing Release of Resource after Effective Lifetime

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Pydantic Pydantic-ai affected >= 2.10.0, < 2.53.0 Not specified
CNA Pydantic Pydantic-ai-slim affected >= 2.10.0, < 2.53.0 Not specified

References

ReferenceSourceLinkTags
github.com/pydantic/pydantic-ai/security/advisories/GHSA-6fqq-452j-qhrp [email protected] github.com
github.com/pydantic/pydantic-ai/releases/tag/v2.53.0 [email protected] github.com
github.com/pydantic/pydantic-ai/commit/453f19feeb7ab1d789f9393b1723c6a73... [email protected] github.com
github.com/pydantic/pydantic-ai/pull/9478 [email protected] github.com
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