How severe is CVE-2021-39221?

CVE-2021-39221 has a CVSS 3.x base score of 6.4, rated medium severity. It is exploitable over network with high attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2021-39221 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (39th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-39221?

CVE-2021-39221 affects Nextcloud Contacts. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-39221?

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

When was CVE-2021-39221 published?

CVE-2021-39221 was published on 2021-10-25 and last updated on 2026-06-17.

CVE-2021-39221

CVE-2021-39221 is a medium-severity vulnerability in Nextcloud Contacts 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-79.

Key facts

Severity: Medium (CVSS 3.x base score 6.4)
CVSS v2: 3.5
EPSS exploit prediction: 1% (39th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Nextcloud Contacts
Published: 2021-10-25
Last modified: 2026-06-17

Description

Nextcloud is an open-source, self-hosted productivity platform. The Nextcloud Contacts application prior to version 4.0.3 was vulnerable to a stored Cross-Site Scripting (XSS) vulnerability. For exploitation, a user would need to right-click on a malicious file and open the file in a new tab. Due the strict Content-Security-Policy shipped with Nextcloud, this issue is not exploitable on modern browsers supporting Content-Security-Policy. It is recommended that the Nextcloud Contacts application is upgraded to 4.0.3. As a workaround, one may use a browser that has support for Content-Security-Policy.

Frequently asked questions

What is CVE-2021-39221?: Nextcloud is an open-source, self-hosted productivity platform. The Nextcloud Contacts application prior to version 4.0.3 was vulnerable to a stored Cross-Site Scripting (XSS) vulnerability. For exploitation, a user would need to right-click on a malicious file and open the file in a new tab. Due the strict Content-Security-Policy shipped with Nextcloud, this issue is not exploitable on modern browsers supporting Content-Security-Policy. It is recommended that the Nextcloud Contacts application is upgraded to 4.0.3. As a workaround, one may use a browser that has support for Content-Security-Policy.
How severe is CVE-2021-39221?: CVE-2021-39221 has a CVSS 3.x base score of 6.4, rated medium severity. It is exploitable over network with high attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2021-39221 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (39th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-39221?: CVE-2021-39221 affects Nextcloud Contacts. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-39221?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-39221 published?: CVE-2021-39221 was published on 2021-10-25 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:nextcloud:contacts:*:*:*:*:*:*:*:*

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