{"id":"CVE-2026-107286","state":"PUBLISHED","title":"Pydantic AI: Concurrency-limited models can keep their slot when a streamed request ends early","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.","publishedAt":"2026-10-08T15:12:26.597Z","updatedAt":"2026-10-08T17:27:24.185Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","source":"GitHub_M"},"assigner":"GitHub_M","products":["pydantic pydantic-ai","pydantic pydantic-ai-slim"],"affected":[{"vendor":"pydantic","product":"pydantic-ai","versions":[{"version":">= 2.10.0, < 2.53.0","status":"affected"}]},{"vendor":"pydantic","product":"pydantic-ai-slim","versions":[{"version":">= 2.10.0, < 2.53.0","status":"affected"}]}],"references":["https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-6fqq-452j-qhrp","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"],"weaknesses":["CWE-772"],"ingestedAt":"2026-10-29T20:10:23.711Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/107xxx/CVE-2026-107286.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-107286","state":"PUBLISHED","datePublished":"2026-10-08T15:12:26.597Z","dateUpdated":"2026-10-08T17:27:24.185Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-10-07T15:53:23.586Z"},"containers":{"cna":{"title":"Pydantic AI: Concurrency-limited models can keep their slot when a streamed request ends early","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"pydantic","product":"pydantic-ai","versions":[{"version":">= 2.10.0, < 2.53.0","status":"affected"}]},{"vendor":"pydantic","product":"pydantic-ai-slim","versions":[{"version":">= 2.10.0, < 2.53.0","status":"affected"}]}],"references":[{"url":"https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-6fqq-452j-qhrp","name":"https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-6fqq-452j-qhrp","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/pydantic/pydantic-ai/pull/9478","name":"https://github.com/pydantic/pydantic-ai/pull/9478","tags":["x_refsource_MISC"]},{"url":"https://github.com/pydantic/pydantic-ai/commit/453f19feeb7ab1d789f9393b1723c6a73b3d77b2","name":"https://github.com/pydantic/pydantic-ai/commit/453f19feeb7ab1d789f9393b1723c6a73b3d77b2","tags":["x_refsource_MISC"]},{"url":"https://github.com/pydantic/pydantic-ai/releases/tag/v2.53.0","name":"https://github.com/pydantic/pydantic-ai/releases/tag/v2.53.0","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-772","lang":"en","description":"CWE-772: Missing Release of Resource after Effective Lifetime","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-10-08T15:12:26.597Z"},"source":{"advisory":"GHSA-6fqq-452j-qhrp","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-08T17:26:50.651820Z","id":"CVE-2026-107286","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-08T17:27:24.185Z"}}]}}}