How severe is CVE-2021-23836?

CVE-2021-23836 has a CVSS 3.x base score of 4.8, rated medium severity. It is exploitable over network with low attack complexity, requires high privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2021-23836 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (56th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-23836?

CVE-2021-23836 affects Flatcore. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-23836?

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

When was CVE-2021-23836 published?

CVE-2021-23836 was published on 2021-01-15 and last updated on 2026-06-17.

CVE-2021-23836

CVE-2021-23836 is a medium-severity vulnerability in Flatcore with a CVSS 3.x base score of 4.8. 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-79.

Key facts

Severity: Medium (CVSS 3.x base score 4.8)
CVSS v2: 3.5
EPSS exploit prediction: 1% (56th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Flatcore
Published: 2021-01-15
Last modified: 2026-06-17

Description

An issue was discovered in flatCore before 2.0.0 build 139. A stored XSS vulnerability was identified in the prefs_smtp_psw HTTP request body parameter for the acp interface. An admin user can inject malicious client-side script into the affected parameter without any form of input sanitization. The injected payload will be executed in the browser of a user whenever one visits the affected module page.

Frequently asked questions

What is CVE-2021-23836?: An issue was discovered in flatCore before 2.0.0 build 139. A stored XSS vulnerability was identified in the prefs_smtp_psw HTTP request body parameter for the acp interface. An admin user can inject malicious client-side script into the affected parameter without any form of input sanitization. The injected payload will be executed in the browser of a user whenever one visits the affected module page.
How severe is CVE-2021-23836?: CVE-2021-23836 has a CVSS 3.x base score of 4.8, rated medium severity. It is exploitable over network with low attack complexity, requires high privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-23836 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (56th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-23836?: CVE-2021-23836 affects Flatcore. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-23836?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-23836 published?: CVE-2021-23836 was published on 2021-01-15 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:flatcore:flatcore:*:*:*:*:*:*:*:*

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