Auth bypass in 9001 Copyparty

CVE-2026-70657

Copyparty is a portable file server. Prior to 1.20.17, copyparty volumes with the dk or dks directory-key flag combined with the fk or fka file-key flag can convert a valid file key into a directory key, granting read access to the containing folder. This vulnerability was only reachable if both types of keys (filekeys and dirkeys) were manually enabled in the volume flags simultaneously. This issue is fixed in version 1.20.17.

Vulnerability class: Broken Access Control

Published · last modified .

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N.

EPSS exploit prediction

EPSS: 0.003 (23.9th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 24th percentile — 23.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-70657: held from 0.003 to 0.003.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: +0.000

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-70657?
CVE-2026-70657 is a medium-severity vulnerability in 9001 Copyparty, classified under Incorrect Authorization. CVSS score: 4.3/10. Published 2026-08-18.
How severe is CVE-2026-70657?
Medium severity. CVSS v3 base score is 4.3 out of 10.