CVE-2026-27948 Copyparty vulnerable to eflected cross-site scripting via setck parameter

What is CVE-2026-27948?

CVE-2026-27948 is a medium-severity cross-site scripting vulnerability in 9001 copyparty, published on 26 Feb 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

Copyparty is a portable file server. In versions prior to 1.20.9, an XSS allows for reflected cross-site scripting via URL-parameter `?setck=...`. Version 1.20.9 fixes the issue.

Weakness: CWE-79

Which versions are affected by CVE-2026-27948?

3 open source packages ship an affected version, including copyparty. It affects 1 product.

Products include 9001 Copyparty.

How do I fix CVE-2026-27948?

Upgrade copyparty to 1.20.9 or later.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2026-27948 being exploited?

There is no known exploitation of CVE-2026-27948 in the wild and no public exploit code.

Other vulnerabilities in 9001 copyparty

• CVE-2023-41471 Cross-site scripting in n/a High 7.8
• CVE-2025-54796 Copyparty is vulnerable to Regex Denial of Service (ReDoS) attacks through "Recent Uploads" page High 7.5
• CVE-2023-37474 Path traversal in copyparty High 7.5
• CVE-2025-54589 copyparty Reflected XSS via Filter Parameter Medium 6.3
• CVE-2023-38501 copyparty vulnerable to reflected cross-site scripting via k304 parameter Medium 6.3

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-62cr-6wp5-q43h, PYSEC-2026-2136.