{"id":"CVE-2026-107288","state":"PUBLISHED","title":"Pydantic AI: web_fetch_tool blocked_domains bypass via a hostname the resolver normalizes differently","description":"Pydantic AI is a Python agent framework for building applications and workflows with Generative AI. From 1.77.0 until 1.107.6 and 2.44.0, the local web_fetch_tool and the WebFetch local fallback compare blocked_domains entries with a URL hostname before both values are normalized to the form used by getaddrinfo. An attacker-influenced model can use an equivalent IDNA spelling, non-ASCII label separator, case variation, or trailing root label that resolves to a blocked host but does not match the configured string, causing the application to fetch that host with its own privileges. allowed_domains fails closed for unmatched spellings, and private-IP and cloud-metadata protections remain effective. This issue is fixed in versions 1.107.6 and 2.44.0.","publishedAt":"2026-10-08T15:18:40.047Z","updatedAt":"2026-10-08T17:28:53.801Z","severity":{"score":3.7,"label":"Low","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["pydantic pydantic-ai","pydantic pydantic-ai-slim"],"affected":[{"vendor":"pydantic","product":"pydantic-ai","versions":[{"version":">= 1.77.0, < 1.107.6","status":"affected"},{"version":">= 2.0.0b1, < 2.44.0","status":"affected"}]},{"vendor":"pydantic","product":"pydantic-ai-slim","versions":[{"version":">= 1.77.0, < 1.107.6","status":"affected"},{"version":">= 2.0.0b1, < 2.44.0","status":"affected"}]}],"references":["https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-22h6-qm39-v87j","https://github.com/pydantic/pydantic-ai/pull/8407","https://github.com/pydantic/pydantic-ai/pull/8409","https://github.com/pydantic/pydantic-ai/pull/8421","https://github.com/pydantic/pydantic-ai/commit/490335f8e2322e143a79337ddca9410e0176c812","https://github.com/pydantic/pydantic-ai/commit/a9dab92099d0ef9d5d4aa34ccac8a6f1b0e51284","https://github.com/pydantic/pydantic-ai/commit/c1f212a084cbfa0012f2044cdb4731d214b3b983","https://github.com/pydantic/pydantic-ai/releases/tag/v1.107.6","https://github.com/pydantic/pydantic-ai/releases/tag/v2.44.0"],"weaknesses":["CWE-918","CWE-1289"],"ingestedAt":"2026-10-29T20:10:23.711Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/107xxx/CVE-2026-107288.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-107288","state":"PUBLISHED","datePublished":"2026-10-08T15:18:40.047Z","dateUpdated":"2026-10-08T17:28:53.801Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-10-07T15:53:23.586Z"},"containers":{"cna":{"title":"Pydantic AI: web_fetch_tool blocked_domains bypass via a hostname the resolver normalizes differently","descriptions":[{"lang":"en","value":"Pydantic AI is a Python agent framework for building applications and workflows with Generative AI. From 1.77.0 until 1.107.6 and 2.44.0, the local web_fetch_tool and the WebFetch local fallback compare blocked_domains entries with a URL hostname before both values are normalized to the form used by getaddrinfo. An attacker-influenced model can use an equivalent IDNA spelling, non-ASCII label separator, case variation, or trailing root label that resolves to a blocked host but does not match the configured string, causing the application to fetch that host with its own privileges. allowed_domains fails closed for unmatched spellings, and private-IP and cloud-metadata protections remain effective. This issue is fixed in versions 1.107.6 and 2.44.0."}],"affected":[{"vendor":"pydantic","product":"pydantic-ai","versions":[{"version":">= 1.77.0, < 1.107.6","status":"affected"},{"version":">= 2.0.0b1, < 2.44.0","status":"affected"}]},{"vendor":"pydantic","product":"pydantic-ai-slim","versions":[{"version":">= 1.77.0, < 1.107.6","status":"affected"},{"version":">= 2.0.0b1, < 2.44.0","status":"affected"}]}],"references":[{"url":"https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-22h6-qm39-v87j","name":"https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-22h6-qm39-v87j","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/pydantic/pydantic-ai/pull/8407","name":"https://github.com/pydantic/pydantic-ai/pull/8407","tags":["x_refsource_MISC"]},{"url":"https://github.com/pydantic/pydantic-ai/pull/8409","name":"https://github.com/pydantic/pydantic-ai/pull/8409","tags":["x_refsource_MISC"]},{"url":"https://github.com/pydantic/pydantic-ai/pull/8421","name":"https://github.com/pydantic/pydantic-ai/pull/8421","tags":["x_refsource_MISC"]},{"url":"https://github.com/pydantic/pydantic-ai/commit/490335f8e2322e143a79337ddca9410e0176c812","name":"https://github.com/pydantic/pydantic-ai/commit/490335f8e2322e143a79337ddca9410e0176c812","tags":["x_refsource_MISC"]},{"url":"https://github.com/pydantic/pydantic-ai/commit/a9dab92099d0ef9d5d4aa34ccac8a6f1b0e51284","name":"https://github.com/pydantic/pydantic-ai/commit/a9dab92099d0ef9d5d4aa34ccac8a6f1b0e51284","tags":["x_refsource_MISC"]},{"url":"https://github.com/pydantic/pydantic-ai/commit/c1f212a084cbfa0012f2044cdb4731d214b3b983","name":"https://github.com/pydantic/pydantic-ai/commit/c1f212a084cbfa0012f2044cdb4731d214b3b983","tags":["x_refsource_MISC"]},{"url":"https://github.com/pydantic/pydantic-ai/releases/tag/v1.107.6","name":"https://github.com/pydantic/pydantic-ai/releases/tag/v1.107.6","tags":["x_refsource_MISC"]},{"url":"https://github.com/pydantic/pydantic-ai/releases/tag/v2.44.0","name":"https://github.com/pydantic/pydantic-ai/releases/tag/v2.44.0","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":3.7,"baseSeverity":"LOW","confidentialityImpact":"LOW","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-918","lang":"en","description":"CWE-918: Server-Side Request Forgery (SSRF)","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-1289","lang":"en","description":"CWE-1289: Improper Validation of Unsafe Equivalence in Input","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-10-08T15:18:40.047Z"},"source":{"advisory":"GHSA-22h6-qm39-v87j","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-08T17:28:31.014859Z","id":"CVE-2026-107288","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-08T17:28:53.801Z"}}]}}}