7.5

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

Analyzed
AliasesGHSA-6fqq-452j-qhrpPYSEC-2026-4276PYSEC-2026-4285
Published 08-10-2026Last modified 08-10-2026

Vulnerability summary

CVE-2026-107286 is a high (CVSS 7.5) vulnerability in pydantic pydantic_ai. EPSS estimates a 0.45% chance of exploitation in the next 30 days, higher than 39.1% of scored vulnerabilities.

Priority
Prioritisesevere

Severe, CVSS 7.5 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 0% (FIRST, 03-11-2026)

Source freshness unavailable

How is this decided?
CVSS score
7.5/10
010
High · v3.1 (CVE.org)
EPSS score
0.45%
0%100%
Low · Change unavailable
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Timeline

  1. 08-10-2026
    PublishedVulnerability first disclosed.
  2. 08-10-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

3 scores · 3 sources · 1 version

EPSS trend

Probability

0.45%

Chance of exploitation in the next 30 days

Percentile

39%

Versus all other CVEs

30-day change

Change unavailable

Change unavailable

09-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Pydantic3 products
PyPI2 products
  • pydantic-ai≥ 2.10.0, < 2.53.0
  • pydantic-ai-slim≥ 2.10.0, < 2.53.0

2 vendors · 5 products

References

9 links