CVE-2021-21264 Bypass of fix for CVE-2020-26231, Twig sandbox escape
Authenticated users can bypass Twig sandbox restrictions to execute arbitrary PHP code if safe mode is enabled.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2021-21264?
CVE-2021-21264 is a medium-severity code injection vulnerability in Octobercms October, published on 3 May 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
October is a free, open-source, self-hosted CMS platform based on the Laravel PHP Framework. A bypass of CVE-2020-26231 (fixed in 1.0.470/471 and 1.1.1) was discovered that has the same impact as CVE-2020-26231 & CVE-2020-15247. An authenticated backend user with the `cms.manage_pages`, `cms.manage_layouts`, or `cms.manage_partials` permissions who would **normally** not be permitted to provide PHP code to be executed by the CMS due to `cms.enableSafeMode` being enabled is able to write specific Twig code to escape the Twig sandbox and execute arbitrary PHP. This is not a problem for anyone that trusts their users with those permissions to normally write & manage PHP within the CMS by not having `cms.enableSafeMode` enabled, but would be a problem for anyone relying on `cms.enableSafeMode` to ensure that users with those permissions in production do not have access to write & execute arbitrary PHP. Issue has been patched in Build 472 (v1.0.472) and v1.1.2. As a workaround, apply https://github.com/octobercms/october/commit/f63519ff1e8d375df30deba63156a2fc97aa9ee7 to your installation manually if unable to upgrade to Build 472 or v1.1.2.
Weakness: CWE-862
Which versions are affected by CVE-2021-21264?
4 open source packages ship an affected version, including october/cms. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
october/cms Packagist | From 1.0.471 | 1.0.472 |
october/cms Packagist | From 1.0.471 | 1.0.472 |
october/cms Packagist | From 1.1.1 | 1.1.2 |
october/cms Packagist | From 1.1.1 | 1.1.2 |
Products include Octobercms October.
How do I fix CVE-2021-21264?
Upgrade october/cms to a fixed version for your release line: 1.0.472 or 1.1.2.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2021-21264 being exploited?
There is no known exploitation of CVE-2021-21264 in the wild and no public exploit code.
Other vulnerabilities in Octobercms October
Sources
Also known as GHSA-fcr8-6q7r-m4wg.