CVE-2026-32109 Copyparty has unexpected JavaScript execution via crafted URL to folder with `.prologue.html`

What is CVE-2026-32109?

CVE-2026-32109 is a low-severity cross-site scripting vulnerability in 9001 copyparty, published on 11 Mar 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

Official description

Copyparty is a portable file server. Prior to 1.20.12, if an attacker has been given both read- and write-permissions to the server, they can upload a malicious file with the filename .prologue.html and then craft a link to potentially execute arbitrary JavaScript in the victim's context. Note that it is intended behavior that the JavaScript would execute if the target clicks a link to the HTML file itself; "https://example.com/foo/.prologue.html". The vulnerability is that "https://example.com/foo/?b" would also evaluate the file, making the behavior unexpected. There are existing preventative measures (strict SameSite cookies) which makes it harder to leverage this vulnerability in an attack; in order to gain control of the target's authenticated session, the link must be clicked from a page served by the server itself -- most likely by editing an existing resource, which would require additional access permissions. Finally, for this attack to be successful, the attacker's target must click the specific crafted link given by the attacker. This vulnerability is not activated by normally browsing the web-UI on the server. This vulnerability is fixed in 1.20.12.

Weakness: CWE-79

Which versions are affected by CVE-2026-32109?

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

Products include 9001 Copyparty.

How do I fix CVE-2026-32109?

Upgrade copyparty to 1.20.12 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-2026-32109 being exploited?

There is no known exploitation of CVE-2026-32109 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-rcp6-88mm-9vgf, PYSEC-2026-32.