Summary
pydantic-ai: SSRF blocklist bypass via IPv4-compatible, SIIT/IVI, and local NAT64 IPv6 addresses (incomplete fix of CVE-2026-46678)
Full technical description
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 / CVE-2026-46678 (itself a follow-up to 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 webVercelAIAdapterAGUIAdapter/Agent.to_ag_ui
Applications that only download from developer-controlled URLs are not affected.
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.
Impact
Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.
CVE-2026-48782 has a CVSS score of 6.8 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.102.0, 2.0.0b3); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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See it in your environmentNew to Kodem? Get a demo →Remediation advice
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.
Frequently Asked Questions
- What is CVE-2026-48782? CVE-2026-48782 is a medium-severity server-side request forgery (SSRF) vulnerability in pydantic-ai-slim (pip), affecting versions >= 1.56.0, < 1.102.0. It is fixed in 1.102.0, 2.0.0b3. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
- How severe is CVE-2026-48782? CVE-2026-48782 has a CVSS score of 6.8 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which packages are affected by CVE-2026-48782?
pydantic-ai-slim(pip) (versions >= 1.56.0, < 1.102.0)pydantic-ai(pip) (versions >= 1.56.0, < 1.102.0)
- Is there a fix for CVE-2026-48782? Yes. CVE-2026-48782 is fixed in 1.102.0, 2.0.0b3. Upgrade to this version or later.
- Is CVE-2026-48782 exploitable, and should I be worried? Whether CVE-2026-48782 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-48782 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-48782?
- Upgrade
pydantic-ai-slimto 1.102.0 or later - Upgrade
pydantic-aito 1.102.0 or later - Upgrade
pydantic-aito 2.0.0b3 or later - Upgrade
pydantic-ai-slimto 2.0.0b3 or later
- Upgrade