CVE-2026-107286 · GHSA-6fqq-452j-qhrp
Pydantic AI: Concurrency-limited models can keep their slot when a streamed request ends early
- Risk score
- 63/100
- CVSS
- 7.5 v3.1
- Exploit chance (30 days)
- 0.4%
- Published
- 8 Oct 2026
Open in the live forecast Today's forecast
What to know
- What it is
- 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 borrowin…
- Affected
- pydantic-ai (pip) >= 2.10.0, < 2.53.0; pydantic-ai-slim (pip) >= 2.10.0, < 2.53.0
- Fix
- Upgrade pydantic-ai to 2.53.0; pydantic-ai-slim to 2.53.0 or later.
- Exploitation
- No known exploitation
Why it is Amber
- CVSS 7.5 high
- Remotely exploitable without logging in
- On your watchlist: PyPI
Affected packages
| Package | Ecosystem | Vulnerable | Fixed in |
|---|---|---|---|
| pydantic-ai | pip | >= 2.10.0, < 2.53.0 | 2.53.0 |
| pydantic-ai-slim | pip | >= 2.10.0, < 2.53.0 | 2.53.0 |
References
- https://github.com/advisories/GHSA-6fqq-452j-qhrp
- https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-6fqq-452j-qhrp
- https://nvd.nist.gov/vuln/detail/CVE-2026-107286
- https://github.com/pydantic/pydantic-ai/pull/9478
- https://github.com/pydantic/pydantic-ai/commit/453f19feeb7ab1d789f9393b1723c6a73b3d77b2
- https://github.com/pydantic/pydantic-ai/releases/tag/v2.53.0
- https://github.com/advisories/GHSA-6fqq-452j-qhrp
Original description
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.
Last activity 8 Oct 2026. Patch Forecast updates every hour.