CVE-2026-25580: Pydantic AI SSRF via IPv6-encoded Address Bypass

Vulnerability Overview Vulnerability Name: SSRF cloud-metadata blocklist bypass via IPv6-encoded address forms Vulnerability Description: When an application uses Pydantic AI's with set, the cloud metadata blocklist can be bypassed by encoding metadata IPs into IPv6 transliteration forms (such as IPv4-mapped IPv6, IPv6, or NAT64). This causes dual-stack and translation networks to route the IPv6 wrapper to the underlying IPv4 endpoint, exposing cloud IAM short-term credentials. Severity: Medium (CVSS 3.1 Score: 6.8) CVE ID: CVE-2026-25580 CWE ID: CWE-918 (Server-Side Request Forgery (SSRF)) Scope of Impact Affected Versions: : >= 1.56.0, = 1.56.0, < 1.99.0 Fixed Versions: : 1.99.0 : 1.99.0 Conditions for Impact: The application explicitly uses and sets The URL may be influenced by untrusted input Conditions for Non-Impact: Applications using bundled integrations to ingest user input (as they do not propagate from external data) Remediation Fix: Upgrade to version 1.99.0 or higher. The cloud metadata and private IP blocklists now apply to IPv6 transliteration forms (IPv4-mapped IPv6, IPv6, and NAT64 known prefixes) that route to blocked IPv4 endpoints. The blocklist has also been extended to cover additional IANA-assigned IPv4 and IPv6 special-purpose ranges. Workarounds for Unfixed Versions: Avoid forcing on any URLs that may be influenced by untrusted input. If necessary, manually resolve hostnames and validate the results against your own metadata blocklist—including IPv6 encoded forms—before constructing the . Additional Information Reporter: @hondo Publication Date: May 21, 2024 CVSS v3 Base Metrics: Attack Vector: Network Attack Complexity: High Privileges Required: None User Interaction: None Scope: Changed Confidentiality: High Integrity: None Availability: None CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N Related CVE: CVE-2026-25580 Related CWE: CWE-918 Related Resources: GitHub Repository Pydantic AI Documentation

Goal Reached Thanks to every supporter — we hit 100%!

CVE-2026-25580: Pydantic AI SSRF via IPv6-encoded Address Bypass

More from this source