How severe is CVE-2021-40100?

CVE-2021-40100 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2021-40100 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (39th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-40100?

CVE-2021-40100 affects Concretecms Concrete Cms. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-40100?

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

When was CVE-2021-40100 published?

CVE-2021-40100 was published on 2021-09-24 and last updated on 2026-06-17.

CVE-2021-40100

CVE-2021-40100 is a medium-severity vulnerability in Concretecms Concrete Cms with a CVSS 3.x base score of 5.4. 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-79.

Key facts

Severity: Medium (CVSS 3.x base score 5.4)
CVSS v2: 3.5
EPSS exploit prediction: 0% (39th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Concretecms Concrete Cms
Published: 2021-09-24
Last modified: 2026-06-17

Description

An issue was discovered in Concrete CMS through 8.5.5. Stored XSS can occur in Conversations when the Active Conversation Editor is set to Rich Text.

Frequently asked questions

What is CVE-2021-40100?: An issue was discovered in Concrete CMS through 8.5.5. Stored XSS can occur in Conversations when the Active Conversation Editor is set to Rich Text.
How severe is CVE-2021-40100?: CVE-2021-40100 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-40100 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (39th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-40100?: CVE-2021-40100 affects Concretecms Concrete Cms. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-40100?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-40100 published?: CVE-2021-40100 was published on 2021-09-24 and last updated on 2026-06-17.

References

Affected products (1)

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

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