CVE-2026-107286
Pydantic AI: Concurrency-limited models can keep their slot when a streamed request ends early
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
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.
Timeline
ID reserved
By GitHub_M
- 1 day later
· 1 day later
Published
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| NVDNVD · Analyzed | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.45% · top 61% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: yes · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.
Weakness
Affected products
- affected >= 2.10.0, < 2.53.0
- affected >= 2.10.0, < 2.53.0
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- PyPIpydantic-aiGHSA-6fqq-452j-qhrp (opens in a new tab)
- PyPIpydantic-ai-slimGHSA-6fqq-452j-qhrp (opens in a new tab)
References (4)
- https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-6fqq-452j-qhrp (opens in a new tab)x_refsource_CONFIRM
- https://github.com/pydantic/pydantic-ai/pull/9478 (opens in a new tab)x_refsource_MISC
- https://github.com/pydantic/pydantic-ai/commit/453f19feeb7ab1d789f9393b1723c6a73b3d77b2 (opens in a new tab)x_refsource_MISC
- https://github.com/pydantic/pydantic-ai/releases/tag/v2.53.0 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-6fqq-452j-qhrp (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-107286)Record last updated .