craftcms/cms security advisory

CVE-2026-27127: Craft CMS has Cloud Metadata SSRF Protection Bypass via DNS Rebinding

CVE-2026-27127 is a high-severity SSRF vulnerability in the PHP package craftcms/cms (CVSS 6.3), published 24 February 2026. The advisory does not name a fixed version. Exploiting it needs a low-privilege user account.

high 6.3 published 2026-02-24 · updated 2026-06-17

Affected versions: >= 3.5.0, <= 4.16.18
>= 5.0.0-RC1, <= 5.8.22
Fixed in: not stated
Newest release: 5.12.0
Severity: High · CVSS 6.3
Type: Server-side request forgery (SSRF)
CWE-367
Exploited in the wild: Not on the CISA KEV list
checked 2026-11-04

Is your craftcms/cms version affected?

Run composer show craftcms/cms in your project, then enter the version. We check it against this and every other known craftcms/cms advisory.

Who can exploit CVE-2026-27127

Access: A normal, low-privilege user account in the app.
Conditions: It only works under specific conditions the attacker does not fully control (CVSS rates the attack as high complexity).

CVSS vector (scored by NVD): CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N

Your app is only exposed if it uses the affected part of craftcms/cms. The advisory below says which part that is. If you are not sure, upgrade anyway: it costs less than finding out.

How to fix CVE-2026-27127 in craftcms/cms

Find the installed version: composer show craftcms/cms. If you never required it yourself, composer why craftcms/cms shows which package pulls it in.
Update it: composer update craftcms/cms --with-all-dependencies.
If Composer will not go that high, your composer.json constraint is holding it back. Widen it (for example "craftcms/cms": "^5.12.0" if you can take that version), or upgrade the package that requires it.
Run composer audit. It reads the same advisory data and should no longer list CVE-2026-27127.
Commit composer.lock and deploy it. On the server, run composer install --no-dev from the lock file, not composer update.

If you cannot upgrade yet

General hardening for SSRF issues while the upgrade waits. None of it replaces the fix.

Block outbound requests from the app server to private ranges and cloud metadata (169.254.169.254) at the firewall.
Do not pass user-supplied URLs to the affected feature.
If your app does not use the affected feature, note that in your audit, but still plan the upgrade.

The CVE-2026-27127 advisory

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 performs DNS resolution separately from the HTTP request. This Time-of-Check-Time-of-Use (TOCTOU) vulnerability enables DNS rebinding attacks, where an attacker’s DNS server returns different IP addresses for validation compared to the actual request. This is a bypass of the security fix for CVE-2025-68437 that allows access to all blocked IPs, not just IPv6 endpoints. 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.

Description from the CVE record, published by GitHub (the CVE Numbering Authority), via the NVD entry for CVE-2026-27127. Advisory title: “Craft CMS has Cloud Metadata SSRF Protection Bypass via DNS Rebinding”.

References

GitHub advisory GHSA-gp2f-7wcm-5fhx github.com
GitHub security advisory GHSA-x27p-wfqw-hfcc github.com
Fix commit a4cf3fb github.com

Other craftcms/cms advisories

critical Craft CMS: Passkey login accepts replayed WebAuthn assertions 2026-08-07
medium CVE-2026-72779: Craft CMS: Arbitrary file read via SplFileObject in non-sandboxed template contexts 2026-08-06
medium CVE-2026-72782: Craft CMS: Authenticated leak of secret environment variables 2026-08-06
medium CVE-2026-72785: Craft CMS: Authorization bypass: view-only Categories user can modify category structure via structures/move-element 2026-08-06
medium CVE-2026-14794: Craft CMS: Missing authorization check allows non-admin control panel users access to user registration metrics 2026-08-06
low CVE-2026-72783: Craft CMS: Incorrect path validation could potentially lead to path traversal 2026-08-06

Need help patching or upgrading? Laskyr does PHP and Laravel security fixes and upgrades. Tell us what you run and we reply with a plan and a price.

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Where this data comes from

Affected and fixed versions: the Packagist security advisories API (GitHub Advisory Database and FriendsOfPHP), the same data composer audit uses. Synced 2026-11-03.
Description, score, weakness and references: NIST National Vulnerability Database (NVD), checked 2026-11-04. This product uses data from the NVD API but is not endorsed or certified by the NVD.
Exploited-in-the-wild status: the CISA Known Exploited Vulnerabilities catalog, checked 2026-11-04.
Compiled by Daniel Lasek at Laskyr from the sources above. The summary, “who can exploit it”, “how to fix it” and hardening sections are our plain-English reading of the record and are generated from it. The quoted description is the record's own text. Spot an error? Tell us.