# CVE-2021-47955: CouchCMS persistent XSS via SVG file upload in KCFinder

Source: https://junglewise.ai/threats/cve-2021-47955-couchcms-persistent-xss-via-svg-file-upload-in-kcfinder  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-16. Updated: 2026-05-16  
License: CC BY 4.0 with a link back

CVE-2021-47955 · Severity: medium · CVSS 5.4 · Published 2026-05-16

CouchCMS, a content management system designed for web designers, is vulnerable to a security flaw in its file upload system. An authenticated user can upload a specially crafted image file (SVG) containing malicious code. When other users or administrators view or preview this file, the code executes in their browser, potentially allowing the attacker to steal session information or perform actions on behalf of the victim.

Technologies: [Couchcms](https://junglewise.ai/threats/technologies/couchcms). Vendors: [Couchcms](https://junglewise.ai/threats/vendors/couchcms).

## Quick answers

**Is CVE-2021-47955 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2021-47955 being exploited in the wild.

**How severe is CVE-2021-47955?** Medium severity, with a CVSS score of 5.4, published 16 May 2026.

**Which products and versions are affected?** Couchcms 2.2.1.

**Is there a fix for CVE-2021-47955?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2021-47955 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2021-47955?** Check whether you run Couchcms at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A stored cross-site scripting (XSS) vulnerability exists in CouchCMS 2.2.1 due to improper sanitization of uploaded SVG files. Authenticated attackers can utilize the file upload functionality at the /couch/includes/kcfinder/browse.php endpoint to upload SVG files containing embedded <script> tags. Because the application fails to strip JavaScript from SVG XML data, the script executes in the context of any user who subsequently accesses or previews the file. This can lead to session hijacking via cookie theft or unauthorized administrative actions. The vulnerability was originally identified in the KCFinder integration used by the CMS.

## Affected products

- CouchCMS CouchCMS 2.2.1

## Timeline

- 2021-01-25: disclosed: Initial discovery by researcher xxcdd
- 2021-03-11: other: Exploit published on Exploit-DB
- 2026-05-16: advisory: CVE published/updated via VulnCheck and NVD

## References

- [https://github.com/CouchCMS/CouchCMS](https://github.com/CouchCMS/CouchCMS)
- [https://www.exploit-db.com/exploits/49636](https://www.exploit-db.com/exploits/49636)
- [https://www.vulncheck.com/advisories/couchcms-cross-site-scripting-via-svg-file-upload](https://www.vulncheck.com/advisories/couchcms-cross-site-scripting-via-svg-file-upload)

## Related threats

- [CouchCMS SSRF via SVG upload in browse.php](https://junglewise.ai/threats/cve-2021-47958-couchcms-ssrf-via-svg-upload-in-browse-php)
- [CouchCMS privilege escalation via f_k_levels_list parameter tampering](https://junglewise.ai/threats/cve-2026-29002-couchcms-privilege-escalation-via-f-k-levels-list-parameter)
- [A security flaw has been discovered in CouchCMS up to 2.4. Affected is an unknown function of the file…](https://junglewise.ai/threats/cve-2025-15005-a-security-flaw-has-been-discovered-in-couchcms-up-to-2-4)