How severe is CVE-2021-21264?

CVE-2021-21264 has a CVSS 3.x base score of 5.2, rated medium severity. It is exploitable over local access with low attack complexity, requires high privileges and user interaction. Impact on confidentiality is low, integrity low, and availability low.

Is CVE-2021-21264 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-21264?

CVE-2021-21264 affects Octobercms October. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-21264?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-21264 published?

CVE-2021-21264 was published on 2021-05-03 and last updated on 2026-06-17.

CVE-2021-21264

CVE-2021-21264 is a medium-severity vulnerability in Octobercms October with a CVSS 3.x base score of 5.2. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-862.

Key facts

Severity: Medium (CVSS 3.x base score 5.2)
CVSS v2: 4.4
EPSS exploit prediction: 0% (18th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-862
Affected product: Octobercms October
Published: 2021-05-03
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-21264?: 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.
How severe is CVE-2021-21264?: CVE-2021-21264 has a CVSS 3.x base score of 5.2, rated medium severity. It is exploitable over local access with low attack complexity, requires high privileges and user interaction. Impact on confidentiality is low, integrity low, and availability low.
Is CVE-2021-21264 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-21264?: CVE-2021-21264 affects Octobercms October. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-21264?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-21264 published?: CVE-2021-21264 was published on 2021-05-03 and last updated on 2026-06-17.

References

https://github.com/octobercms/october/security/advisories/GHSA-fcr8-6q7r-m4wg

Affected products (1)

cpe:2.3:a:octobercms:october:*:*:*:*:*:*:*:*

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