CVE-2026-48782

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.

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.

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 / 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 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…

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.

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.

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 / 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 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…

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 / 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 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…

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 / 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 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…

Root has patched CVE-2026-48782 in the pydantic-ai-slim package for Root:PyPI. Multiple fixed versions available.