CVE-2026-27129: Cloud Metadata SSRF Protection Bypass via IPv6 Resolution

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-02-24 · updated 2026-06-17
Weakness: CWE-918

Description

Craft is a content management system (CMS). In versions 4.5.0-RC1 through 4.16.18 and 5.0.0-RC1 through 5.8.22, the SSRF validation in Craft CMS’s GraphQL Asset mutation uses `gethostbyname()`, which only resolves IPv4 addresses. When a hostname has only AAAA (IPv6) records, the function returns the hostname string itself, causing the blocklist comparison to always fail and completely bypassing SSRF protection. This is a bypass of the security fix for CVE-2025-68437. Exploitation requires GraphQL schema permissions for editing assets in the `<VolumeName>` volume and creating assets in the `<VolumeName>` volume. These permissions may be granted to authenticated users with appropriate GraphQL schema access and/or Public Schema (if misconfigured with write permissions). Versions 4.16.19 and 5.8.23 patch the issue.

Affected products

craftcms cms: from 3.5.0 before 4.16.19; from 5.0.1 before 5.8.23; 5.0.0, 5.0.0-rc1 — fixed in 4.16.19, 5.8.23

How to fix

Upgrade to a fixed version: craftcms cms 4.16.19, 5.8.23. Check the vendor advisory for mitigations.

References

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