Threat database

## Summary 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 routes the affected IPv6 transition forms (NAT64- or ISATAP-configured networks)**, the cloud-metadata blocklist could be bypassed by encoding the metadata IP in an IPv6 transition form that the previous fix did not decode — IPv4-compatible IPv6 (`::a.b.c.d`), the NAT64 RFC 8215 local-use prefix (`64:ff9b:1::/48`), operator-chosen NAT64 prefixes, or ISATAP. The IPv6 wrapper is then delivered to the underlying IPv4 metadata endpoint, exposing cloud IAM short-term credentials. **The bypass is exploitable only in environments whose network actually routes these 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 them 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](https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-cqp8-fcvh-x7r3) / [CVE-2026-46678](https://nvd.nist.gov/vuln/detail/CVE-2026-46678) (itself a follow-up to [CVE-2026-25580](https://nvd.nist.gov/vuln/detail/CVE-2026-25580)). The prior remediation decoded only IPv4-mapped IPv6, 6to4, and the NAT64 well-known prefix; the metadata guarantee did not hold for the remaining transition forms. ## Severity **MEDIUM** — `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N` = **6.8** Same impact metrics and narrow attack surface as the parent advisory (AC:H): exploitation requires the application to have opted into `allow-local` on a URL influenced by untrusted input, and the NAT64/ISATAP variants additionally require the deployment network to route those forms. **CWE-918**: Server-Side Request Forgery (SSRF) ## Affected Versions | Package | Vulnerable | Patched | |---|---|---| | `pydantic-ai` | `>= 1.56.0, < 1.102.0`; `>= 2.0.0b1, < 2.0.0b3` | `1.102.0`; `2.0.0b3` | | `pydantic-ai-slim` | `>= 1.56.0, < 1.102.0`; `>= 2.0.0b1, < 2.0.0b3` | `1.102.0`; `2.0.0b3` | These transition forms have not been decoded since SSRF protection was introduced in `1.56.0`. ## Who Is Affected Users are affected **only if** their application explicitly opts a `FileUrl` (`ImageUrl`, `AudioUrl`, `VideoUrl`, `DocumentUrl`) into `force_download='allow-local'` on a URL that is, or could be, influenced by untrusted input. Beyond that precondition, the affected encodings only reach a metadata endpoint in environments whose network actually routes them. The broadly-routable IPv4-mapped form was addressed in `1.99.0` (CVE-2026-46678); the additional forms addressed here require a **NAT64-configured network** (IPv6-only or dual-stack-with-NAT64 deployments, including some Kubernetes setups) for the NAT64 variants, or an **ISATAP tunnel** for the ISATAP variant. The IPv4-compatible and Teredo forms are deprecated and not routed by modern stacks; they are addressed as defense-in-depth. Most deployments on a standard dual-stack cloud VM or container are therefore not exploitable in practice, but the fix restores the "always blocked" guarantee for the environments that are. Users are **not** affected if they use any of the bundled integrations to ingest user input, because they do not propagate `force_download` from external data: - `Agent.to_web` / `clai web` - `VercelAIAdapter` - `AGUIAdapter` / `Agent.to_ag_ui` Applications that only download from developer-controlled URLs are not affected. ## Remediation Upgrade to `1.102.0` or later (or `2.0.0b3` or later on the 2.0 pre-release line). The cloud-metadata and private-IP blocklists now decode the embedded IPv4 of every standardized IPv6 transition form before evaluating it — IPv4-mapped, IPv4-compatible, 6to4, NAT64 across all prefix lengths (including the RFC 8215 local-use prefix and operator-chosen prefixes), ISATAP, and Teredo. The set of always-blocked cloud metadata/credential endpoints has also been expanded across providers. ## Workaround for Unpatched Versions Avoid passing `force_download='allow-local'` on any URL that could be influenced by untrusted input. If developers must, resolve the hostname themselves and validate the result against their own metadata blocklist — including IPv6 transition forms — before constructing the `FileUrl`. ## Credits Reported by [@SnailSploit](https://snailsploit.com).

Pydantic AI is a Python agent framework for building applications and workflows with Generative AI. From 0.0.26 to before 1.56.0, aServer-Side Request Forgery (SSRF) vulnerability exists in Pydantic AI's URL download functionality. When applications accept message history from untrusted sources, attackers can include malicious URLs that cause the server to make HTTP requests to internal network resources, potentially accessing internal services or cloud credentials. This vulnerability only affects applications that accept message history from external users. This vulnerability is fixed in 1.56.0.

Pydantic AI is a Python agent framework for building applications and workflows with Generative AI. From 1.34.0 to before 1.51.0, a path traversal vulnerability in the Pydantic AI web UI allows an attacker to serve arbitrary JavaScript in the context of the application by crafting a malicious URL. In affected versions, the CDN URL is constructed using a version query parameter from the request URL. This parameter is not validated, allowing path traversal sequences that cause the server to fetch and serve attacker-controlled HTML/JavaScript from an arbitrary source on the same CDN, instead of the legitimate chat UI package. If a victim clicks the link or visits it via an iframe, attacker-controlled code executes in their browser, enabling theft of chat history and other client-side data. This vulnerability only affects applications that use Agent.to_web to serve a chat interface and clai web to serve a chat interface from the CLI. These are typically run locally (on localhost), but may also be deployed on a remote server. This vulnerability is fixed in 1.51.0.