CVE-2026-48782
pydantic-ai: SSRF blocklist bypass via IPv4-compatible, SIIT/IVI, and local NAT64 IPv6 addresses (incomplete fix of CVE-2026-46678)
Impact
Pydantic AI is a Python agent framework for building applications and workflows with Generative AI. In versions 1.56.0 through 1.101.0, 2.0.0b1, and 2.0.0b2, the cloud-metadata blocklist could be bypassed by encoding the metadata IP in an IPv6 transition form that the previous fix, CVE-2026-46678, did not decode, exposing cloud IAM short-term credentials. The previous remediation decoded only IPv4-mapped IPv6, 6to4, and the NAT64 well-known prefix, so the metadata guarantee did not hold for the remaining transition forms: IPv4-compatible IPv6 (::a.b.c.d), the NAT64 RFC 8215 local-use prefix (64:ff9b:1::/48), operator-chosen NAT64 prefixes, and ISATAP. The IPv6 wrapper is then delivered to the underlying IPv4 metadata endpoint. This occurs when an application using Pydantic AI opts a URL into force_download='allow-local' (which disables the default block on private/internal IPs) and runs on a network that actually routes the affected IPv6 transition forms: NAT64-configured networks (IPv6-only or dual-stack-with-NAT64 deployments, including some Kubernetes setups) for the NAT64 variants, or networks with an ISATAP tunnel for ISATAP. A standard dual-stack cloud VM or container does not route these forms and is not affected in practice. The IPv4-compatible and Teredo variants are deprecated and addressed as defense-in-depth. This is an incomplete fix of GHSA-cqp8-fcvh-x7r3 / CVE-2026-46678 (itself a follow-up to CVE-2026-25580). This issue has been fixed in version 2.0.0b3.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| pip | pydantic-ai-slim | >= 1.56.0, < 1.102.0 | 1.102.0 |
| pip | pydantic-ai | >= 1.56.0, < 1.102.0 | 1.102.0 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Pydantic | Pydantic Ai | from 1.56.0 before 1.102.0 Version 2.0.0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-cg7w-rg45-pc59
- https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-cg7w-rg45-pc59
- https://nvd.nist.gov/vuln/detail/CVE-2026-48782
- https://github.com/pydantic/pydantic-ai/pull/5596
- https://github.com/pydantic/pydantic-ai/commit/1add06179ba4de259f7ab977620b697b7209f7e4
- https://github.com/pydantic/pydantic-ai/releases/tag/v1.102.0