Copyparty vulnerable to reflected XSS via setck parameter

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.4 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

EPSS

• CVE-2026-27948: 0.20% estimated exploitation activity in the next 30 days; percentile 9.43 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary An XSS allows for reflected cross-site scripting via URL-parameter ?setck=... Details A reflected cross-site scripting (XSS) vulnerability could allow an attacker to execute malicious javascript by tricking users into accessing a malicious link. The worst-case outcome of this is being able to move or delete existing files on the server, or upload new files, using the account of the person who clicks the malicious link. Indicators of Compromise All attempted attacks (successful or not) would be logged to both the copyparty serverlog and the accesslog of the reverseproxy, and are detected by grep -E '[?&]setck=[^&"]%' (the text setck= eventually followed by the % character).

Published by the source

26 Feb 2026, 22:33 UTC

Last modified by the source

13 Jul 2026, 07:26 UTC

Source last checked

26 Oct 2026, 13:36 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-62cr-6wp5-q43h

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-62cr-6wp5-q43h

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# Patch Next advisory brief: CVE-2026-27948

Advisory: Copyparty vulnerable to reflected XSS via setck parameter
IDs: CVE-2026-27948, GHSA-62cr-6wp5-q43h
Record: https://patchnext.com/advisories/cve-2026-27948 (revision 2, source checked 26 Oct 2026, 13:36 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: copyparty 1.20.9. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI copyparty: affected < 1.20.9; fixed in 1.20.9

## Suggested inspection (read-only)
- `python -m pip show copyparty`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on copyparty.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-62cr-6wp5-q43h (OSV record GHSA-62cr-6wp5-q43h lists affected ranges: PyPI copyparty >=0 <1.20.9 (fixed))
- Verified: https://github.com/advisories/GHSA-62cr-6wp5-q43h (GitHub-reviewed advisory GHSA-62cr-6wp5-q43h lists affected ranges: PyPI copyparty >=0 <1.20.9)

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