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CVE-2026-107286

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

No known exploitation. EPSS puts it in the 38th percentile. A vendor fix is available.

CVSS 3.17.5HighEPSS percentile38th0.4% chance in 30 daysCISA KEVNot listedNo confirmed exploitation
No public exploit knownFixVendor fixNo build named by the sources

Published Updated Sources: CVE.org, NVD

NVD CVE.org

What to do

The vendor has published a fix. Version details are below where the sources state them.

  • Pydantic-aiAffected: >= 2.10.0, < 2.53.0Upgrade to: not statedStated by: CVE record
  • Pydantic-ai-slimAffected: >= 2.10.0, < 2.53.0Upgrade to: not statedStated by: CVE record

Versions as the sources state them. Full version matrix after sign-in

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What it is

From the CVE record

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.

In plain language

No plain-language summary for this CVE yet.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS38th
CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

0.4% chance of exploitation activity in the next 30 days, which ranks it in the 38th percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

8 events over 5 days, from the signal feeds we watch.

  1. Patch availableworkaround available, record updated
  2. Publishedweakness classified, record updated, record updated, record updated

Affected products

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

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

Scored 7.5 by NVD.

How it is reached

  • Attack Vector NetworkExploitable remotely over the network without any special conditions
  • Attack Complexity LowNo special conditions — the attack can be reliably reproduced
  • Privileges Required NoneNo authentication required — anyone can exploit this
  • User Interaction NoneNo user interaction needed — fully automated exploitation

Scope

  • Scope UnchangedImpact is limited to the vulnerable component itself

Impact if exploited

  • Confidentiality NoneNo confidentiality impact
  • Integrity NoneNo integrity impact
  • Availability HighTotal denial of service — the component is completely unavailable

Weaknesses

Sources

References in the record

And 1 more reference. See all after sign-in

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