{"id":"CVE-2026-107286","summary":"Pydantic AI: Concurrency-limited models can keep their slot when a streamed request ends early","details":"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.","aliases":["GHSA-6fqq-452j-qhrp"],"modified":"2026-10-09T02:52:04.167627762Z","published":"2026-10-08T15:12:26.597Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107286.json","cna_assigner":"GitHub_M","cwe_ids":["CWE-772"]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107286.json"},{"type":"FIX","url":"https://github.com/pydantic/pydantic-ai/commit/453f19feeb7ab1d789f9393b1723c6a73b3d77b2"},{"type":"FIX","url":"https://github.com/pydantic/pydantic-ai/pull/9478"},{"type":"WEB","url":"https://github.com/pydantic/pydantic-ai/releases/tag/v2.53.0"},{"type":"ADVISORY","url":"https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-6fqq-452j-qhrp"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-107286"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/pydantic/pydantic-ai","events":[{"introduced":"d8b95a48466e99963042d2bd3164c6fdc227e6d4"},{"fixed":"b38ab5d955394144296100d3c41599c003973722"}],"database_specific":{"extracted_events":[{"introduced":"2.10.0"},{"fixed":"2.53.0"}],"source":"AFFECTED_FIELD"}}],"versions":["v2.52.0","v2.51.0","v2.50.0","v2.49.0","v2.48.0","v2.47.0","v2.46.0","v2.45.0","v2.44.0","v2.43.0","v2.42.0","v2.41.0","v2.40.0","v2.39.0","v2.38.0","v2.37.0","v2.36.0","v2.35.3","v2.35.1","v2.35.0","v2.34.0","v2.33.0","v2.32.2","v2.32.1","v2.32.0","v2.31.1","v2.31.0","v2.30.0","v2.29.0","v2.28.0","v2.27.1","v2.27.0","v2.26.0","v2.25.0","v2.24.0","v2.23.0","v2.22.0","v2.21.0","v2.20.0","v2.19.0","v2.18.0","v2.17.0","v2.16.0","v2.15.0","v2.14.1","v2.14.0","v2.13.0","v2.12.0","v2.11.0","v2.10.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-107286.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}