Low 3.7Published Oct 8, 2026

CVE-2026-107288Pydantic AI: web_fetch_tool blocked_domains bypass via a hostname the resolver normalizes differently

Updated under an hour ago (Oct 27, 2026, 7:00 PM ET)

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No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

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.

CVSS: 3.7 LOW (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness (CWE): CWE-918, CWE-1289
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Oct 8, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

pydantic pydantic-ai pydantic:ai (from the name)	from 1.77.0, < 1.107.6; from 2.0.0b1, < 2.44.0	CNA record
pydantic pydantic-ai-slim pydantic:ai_slim (from the name)	from 1.77.0, < 1.107.6; from 2.0.0b1, < 2.44.0	CNA record
pydantic pydantic_ai pydantic:pydantic_ai	from 1.77.0 before 1.107.6; from 2.0.0 before 2.44.0	NVD

References

References

https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-22h6-qm39-v87j	x-refsource-confirm, mitigation, vendor-advisory
https://github.com/pydantic/pydantic-ai/pull/8407	x-refsource-misc, patch, vendor-advisory
https://github.com/pydantic/pydantic-ai/pull/8409	x-refsource-misc, patch, vendor-advisory
https://github.com/pydantic/pydantic-ai/pull/8421	x-refsource-misc, patch, vendor-advisory
https://github.com/pydantic/pydantic-ai/commit/490335f8e2322e143a79337ddca9410e0176c812	x-refsource-misc, patch
https://github.com/pydantic/pydantic-ai/commit/a9dab92099d0ef9d5d4aa34ccac8a6f1b0e51284	x-refsource-misc, patch
https://github.com/pydantic/pydantic-ai/commit/c1f212a084cbfa0012f2044cdb4731d214b3b983	x-refsource-misc, patch
https://github.com/pydantic/pydantic-ai/releases/tag/v1.107.6	x-refsource-misc, patch, release-notes, vendor-advisory
https://github.com/pydantic/pydantic-ai/releases/tag/v2.44.0	x-refsource-misc, patch, release-notes, vendor-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.