GHSA-cqp8-fcvh-x7r3: Pydantic AI: SSRF cloud-metadata blocklist bypass via IPv4-mapped IPv6 (Incomplete fix of CVE-2026-25580)
Summary
Pydantic AI had a security flaw where attackers could bypass protections against accessing cloud-metadata endpoints (special internal servers that store sensitive credentials) by encoding the IP address in IPv6 transition forms (IPv4-mapped IPv6, 6to4, or NAT64, which are ways to represent IPv4 addresses using IPv6 format). This flaw only affects applications that explicitly allow local file downloads with the `force_download='allow-local'` setting on URLs that could be influenced by untrusted users.
Solution / Mitigation
Upgrade to Pydantic AI version 1.99.0 or later, which extends the blocklists to cover IPv6 transition forms that route to blocked IPv4 endpoints and adds protection for additional IANA-reserved IP ranges. For unpatched versions, avoid using `force_download='allow-local'` on URLs influenced by untrusted input, or resolve hostnames manually and validate them against your own blocklist including IPv6-encoded forms before creating the FileUrl.
Vulnerability Details
EPSS: 0.0%
Yes
May 21, 2026
Classification
Affected Vendors
Affected Packages
Original source: https://github.com/advisories/GHSA-cqp8-fcvh-x7r3
First tracked: May 21, 2026 at 08:00 PM
Classified by LLM (prompt v3) · confidence: 92%