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Medium, CVSS 6.8amended

Pydantic AI: SSRF cloud-metadata blocklist bypass via IPv6 zone identifiers

CVE-2026-107289GHSA-vmxc-h2x2-jmf3

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (pydantic-ai 2.44.0, 1.107.6; pydantic-ai-slim 2.44.0, 1.107.6), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • PyPI pydantic-ai

    Affected
    >= 1.56.0, < 1.107.6>= 2.0.0b1, < 2.44.0
    Fixed in
    1.107.6, 2.44.0

  • PyPI pydantic-ai-slim

    Affected
    >= 1.56.0, < 1.107.6>= 2.0.0b1, < 2.44.0
    Fixed in
    1.107.6, 2.44.0

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
6.8 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N
EPSS
  • CVE-2026-107289: 0.39% estimated exploitation activity in the next 30 days; percentile 33.19 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary When an application using Pydantic AI opts a URL into local network access — either a FileUrl with forcedownload='allow-local', or webfetchtool(allowlocalurls=True) — the cloud-metadata blocklist could be bypassed by appending an IPv6 zone identifier to a metadata address (for example fd00:ec2::254%251). The host ignores the zone identifier on a destination that is not link-local and delivers the request to the metadata endpoint anyway, exposing cloud IAM short-term credentials. This is an incomplete fix of GHSA-cqp8-fcvh-x7r3 / CVE-2026-46678 and GHSA-cg7w-rg45-pc59 / CVE-2026-48782, themselves follow-ups to CVE-2026-25580. The parent advisory's remediation guaranteed that cloud metadata endpoints are always blocked, even with local access allowed. That guarantee did not hold for zone-scoped spellings of the IPv6 metadata endpoints. Details The cloud-metadata guard compared IPv6 addresses against its blocklist by set membership. Python includes the zone identifier in…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-vmxc-h2x2-jmf3

  2. Revision 2 · amended ·

    Amended from osv record GHSA-vmxc-h2x2-jmf3

  3. Revision 1 · created ·

    Published from ghsa record GHSA-vmxc-h2x2-jmf3

Agent brief

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# Patch Next advisory brief: CVE-2026-107289

Advisory: Pydantic AI: SSRF cloud-metadata blocklist bypass via IPv6 zone identifiers
IDs: CVE-2026-107289, GHSA-vmxc-h2x2-jmf3
Record: https://patchnext.com/advisories/cve-2026-107289 (revision 3, source checked 26 Oct 2026, 13:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: pydantic-ai 2.44.0, 1.107.6; pydantic-ai-slim 2.44.0, 1.107.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI pydantic-ai: affected >= 1.56.0, < 1.107.6; >= 2.0.0b1, < 2.44.0; fixed in 1.107.6, 2.44.0
- PyPI pydantic-ai-slim: affected >= 1.56.0, < 1.107.6; >= 2.0.0b1, < 2.44.0; fixed in 1.107.6, 2.44.0

## Suggested inspection (read-only)
- `python -m pip show pydantic-ai`: prints the installed version. Run with the environment that serves production active.
- `python -m pip show pydantic-ai-slim`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on pydantic-ai, pydantic-ai-slim.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-vmxc-h2x2-jmf3 (GitHub-reviewed advisory GHSA-vmxc-h2x2-jmf3 lists affected ranges: PyPI pydantic-ai >=1.56.0 =2.0.0b1 =1.56.0 =2.0.0b1 <2.44.0)
- Verified: https://osv.dev/vulnerability/GHSA-vmxc-h2x2-jmf3 (OSV record GHSA-vmxc-h2x2-jmf3 lists affected ranges: PyPI pydantic-ai >=1.56.0 =2.0.0b1 =1.56.0 =2.0.0b1 <2.44.0 (fixed))

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