CVE-2026-32109 — copyparty
LOWCVE-2026-32109 is a low-severity (CVSS 3.7) Cross-site Scripting (XSS) vulnerability in copyparty. A fix is available for copyparty — see the affected versions and patch details below.
Copyparty has unexpected JavaScript execution via crafted URL to folder with `.prologue.html`
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-32109.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-32109 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
copypartyReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | copyparty | all versions | 1.20.12pip install --upgrade 'copyparty==1.20.12' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for copyparty, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update copyparty to 1.20.12 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-32109 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-32109 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-32109. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-32109 in your dependencies?
O3 Security finds CVE-2026-32109 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.