How severe is CVE-2021-40109?

CVE-2021-40109 has a CVSS 3.x base score of 6.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2021-40109 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (43rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-40109?

CVE-2021-40109 affects Concretecms Concrete Cms. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-40109?

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

When was CVE-2021-40109 published?

CVE-2021-40109 was published on 2021-09-27 and last updated on 2026-06-17.

CVE-2021-40109

CVE-2021-40109 is a medium-severity vulnerability in Concretecms Concrete Cms with a CVSS 3.x base score of 6.4. 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-918.

Key facts

Severity: Medium (CVSS 3.x base score 6.4)
CVSS v2: 5.5
EPSS exploit prediction: 1% (43rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-918
Affected product: Concretecms Concrete Cms
Published: 2021-09-27
Last modified: 2026-06-17

Description

A SSRF issue was discovered in Concrete CMS through 8.5.5. Users can access forbidden files on their local network. A user with permissions to upload files from external sites can upload a URL that redirects to an internal resource of any file type. The redirect is followed and loads the contents of the file from the redirected-to server. Files of disallowed types can be uploaded.

Frequently asked questions

What is CVE-2021-40109?: A SSRF issue was discovered in Concrete CMS through 8.5.5. Users can access forbidden files on their local network. A user with permissions to upload files from external sites can upload a URL that redirects to an internal resource of any file type. The redirect is followed and loads the contents of the file from the redirected-to server. Files of disallowed types can be uploaded.
How severe is CVE-2021-40109?: CVE-2021-40109 has a CVSS 3.x base score of 6.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-40109 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (43rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-40109?: CVE-2021-40109 affects Concretecms Concrete Cms. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-40109?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-40109 published?: CVE-2021-40109 was published on 2021-09-27 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:concretecms:concrete_cms:*:*:*:*:*:*:*:*

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