How severe is CVE-2021-21265?

CVE-2021-21265 has a CVSS 3.x base score of 6.8, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2021-21265 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (75th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-21265?

CVE-2021-21265 affects Octobercms October. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-21265?

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

When was CVE-2021-21265 published?

CVE-2021-21265 was published on 2021-03-10 and last updated on 2026-06-17.

CVE-2021-21265

CVE-2021-21265 is a medium-severity vulnerability in Octobercms October with a CVSS 3.x base score of 6.8. 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-644.

Key facts

Severity: Medium (CVSS 3.x base score 6.8)
CVSS v2: 4.3
EPSS exploit prediction: 2% (75th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-644
Affected product: Octobercms October
Published: 2021-03-10
Last modified: 2026-06-17

Description

October is a free, open-source, self-hosted CMS platform based on the Laravel PHP Framework. In October before version 1.1.2, when running on poorly configured servers (i.e. the server routes any request, regardless of the HOST header to an October CMS instance) the potential exists for Host Header Poisoning attacks to succeed. This has been addressed in version 1.1.2 by adding a feature to allow a set of trusted hosts to be specified in the application. As a workaround one may set the configuration setting cms.linkPolicy to force.

Frequently asked questions

What is CVE-2021-21265?: October is a free, open-source, self-hosted CMS platform based on the Laravel PHP Framework. In October before version 1.1.2, when running on poorly configured servers (i.e. the server routes any request, regardless of the HOST header to an October CMS instance) the potential exists for Host Header Poisoning attacks to succeed. This has been addressed in version 1.1.2 by adding a feature to allow a set of trusted hosts to be specified in the application. As a workaround one may set the configuration setting cms.linkPolicy to force.
How severe is CVE-2021-21265?: CVE-2021-21265 has a CVSS 3.x base score of 6.8, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2021-21265 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (75th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-21265?: CVE-2021-21265 affects Octobercms October. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-21265?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-21265 published?: CVE-2021-21265 was published on 2021-03-10 and last updated on 2026-06-17.

References

Affected products (1)

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

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