CVE-2021-21264

Bypass of fix for CVE-2020-26231, Twig sandbox escape

Workarounds

Apply https://github.com/octobercms/october/commit/f63519ff1e8d375df30deba63156a2fc97aa9ee7 to your installation manually if unable to upgrade to Build 472 or v1.1.2.

References

Reported by ka1n4t

For more information

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Threat assessment:

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.

The application does not perform an authorization check before performing a sensitive operation. Typical impact: unauthorized access to restricted functionality or data.

CVE-2021-21264 has a CVSS score of 5.2 (Medium). The vector is requires local access, high privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.0.472, 1.1.2); upgrading removes the vulnerable code path.

Kodem intelligence

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Issue has been patched in Build 472 (v1.0.472) and v1.1.2.

1. What is CVE-2021-21264? CVE-2021-21264 is a medium-severity missing authorization vulnerability in october/cms (composer), affecting versions = 1.0.471. It is fixed in 1.0.472, 1.1.2. The application does not perform an authorization check before performing a sensitive operation.
2. How severe is CVE-2021-21264? CVE-2021-21264 has a CVSS score of 5.2 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of october/cms are affected by CVE-2021-21264? october/cms (composer) versions = 1.0.471 is affected.
4. Is there a fix for CVE-2021-21264? Yes. CVE-2021-21264 is fixed in 1.0.472, 1.1.2. Upgrade to this version or later.
5. Is CVE-2021-21264 exploitable, and should I be worried? Whether CVE-2021-21264 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2021-21264 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2021-21264?
   • Upgrade october/cms to 1.0.472 or later
   • Upgrade october/cms to 1.1.2 or later

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