Pydantic AI: web_fetch_tool blocked_domains bypass via a hostname the resolver normalizes differently

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-107288
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-08 16:17:04 UTC
Updated2026-10-08 18:17:16 UTC
DescriptionPydantic 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.

Risk And Classification

Primary CVSS: v3.1 3.7 LOW from [email protected]

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

Problem Types: CWE-918 | CWE-1289 | CWE-918 CWE-918: Server-Side Request Forgery (SSRF) | CWE-1289 CWE-1289: Improper Validation of Unsafe Equivalence in Input

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary3.7LOWCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
3.1CNADECLARED3.7LOWCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Pydantic Pydantic-ai affected >= 1.77.0, < 1.107.6 Not specified
CNA Pydantic Pydantic-ai affected >= 2.0.0b1, < 2.44.0 Not specified
CNA Pydantic Pydantic-ai-slim affected >= 1.77.0, < 1.107.6 Not specified
CNA Pydantic Pydantic-ai-slim affected >= 2.0.0b1, < 2.44.0 Not specified

References

ReferenceSourceLinkTags
github.com/pydantic/pydantic-ai/releases/tag/v2.44.0 [email protected] github.com
github.com/pydantic/pydantic-ai/pull/8421 [email protected] github.com
github.com/pydantic/pydantic-ai/security/advisories/GHSA-22h6-qm39-v87j [email protected] github.com
github.com/pydantic/pydantic-ai/pull/8407 [email protected] github.com
github.com/pydantic/pydantic-ai/pull/8409 [email protected] github.com
github.com/pydantic/pydantic-ai/releases/tag/v1.107.6 [email protected] github.com
github.com/pydantic/pydantic-ai/commit/490335f8e2322e143a79337ddca9410e0... [email protected] github.com
github.com/pydantic/pydantic-ai/commit/c1f212a084cbfa0012f2044cdb4731d21... [email protected] github.com
github.com/pydantic/pydantic-ai/commit/a9dab92099d0ef9d5d4aa34ccac8a6f1b... [email protected] github.com
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