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Fencer Intel
low 3.6

CVE-2025-27145 json

copyparty renders unsanitized filenames as HTML when user uploads empty files

published last yr. modified last mo. also EUVD-2025-5073 , GHSA-m2jw-cj8v-937r , PYSEC-2026-1278

cvss
3.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 40%
public exploits
0
none known

Summary

copyparty, a portable file server, has a DOM-based cross-site scripting vulnerability in versions prior to 1.16.15. The vulnerability is considered low-risk. By handing someone a maliciously-named file, and then tricking them into dragging the file into copyparty's Web-UI, an attacker could execute arbitrary javascript with the same privileges as that user. For example, this could give unintended read-access to files owned by that user. The bug is triggered by the drag-drop action itself; it is not necessary to actually initiate the upload. The file must be empty (zero bytes). Note that, as a general-purpose webserver, it is intentionally possible to upload HTML-files with arbitrary javascript in `<script>` tags, which will execute when the file is opened. The difference is that this vulnerability would trigger execution of javascript during the act of uploading, and not when the uploaded file was opened. Version 1.16.15 contains a fix.

Patch / fix

  • pypi copyparty 1.16.15
  • 9001 copyparty 1.16.15
  • copyparty_project copyparty 1.16.15

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
last yr.

Exploit prediction

0.47% chance of exploitation in the next 30 days, higher than 40% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • github.com https://github.com/9001/copyparty/security/advisories/GHSA-m2jw-cj8v-937r referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 3.6 CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
GitHub 3.1 3.6 CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
NVD 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
OSV 3.1 3.6 CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
pypi copyparty
<1.16.15
1.16.15

Affected products

  • 9001 copyparty

Classification

Weakness
  • CWE-83 Improper Neutralization of Script in Attributes in a Web Page
  • CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.