High 7.5Published Oct 8, 2026

CVE-2026-107286Pydantic AI: Concurrency-limited models can keep their slot when a streamed request ends early

Updated under an hour ago (2026-10-19 08:23 UTC)

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It affects pydantic-ai and 2 other products. Add what you run to find out whether that includes you.

EPSS puts the chance of exploitation in the next 30 days at 0.45%, higher than 38% of scored CVEs.

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Exploited in the last 30 days

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.

CVSS: 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-772
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): 0.45% (percentile 38)
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Oct 8, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

pydantic pydantic-ai pydantic:ai (from the name)	from 2.10.0, < 2.53.0	CNA record
pydantic pydantic-ai-slim pydantic:ai_slim (from the name)	from 2.10.0, < 2.53.0	CNA record
pydantic pydantic_ai pydantic:pydantic_ai	from 2.10.0 before 2.53.0	NVD

References

https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-6fqq-452j-qhrpx-refsource-confirm, mitigation, vendor-advisory
https://github.com/pydantic/pydantic-ai/pull/9478x-refsource-misc, patch, vendor-advisory
https://github.com/pydantic/pydantic-ai/commit/453f19feeb7ab1d789f9393b1723c6a73b3d77b2x-refsource-misc, patch
https://github.com/pydantic/pydantic-ai/releases/tag/v2.53.0x-refsource-misc, patch, release-notes, vendor-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.