CVE-2021-26566
Synology
- Published
- 26 February 2021
- Last modified
- 17 June 2026
- CVSS
- 9.0 v3.1
- Severity
- critical
- EPSS
- 1.5% (72th pct)
- CISA KEV
- Not listed
- NVD status
- Modified
- Weaknesses
- CWE-201, CWE-200
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Description
Insertion of sensitive information into sent data vulnerability in synorelayd in Synology DiskStation Manager (DSM) before 6.2.3-25426-3 allows man-in-the-middle attackers to execute arbitrary commands via inbound QuickConnect traffic.
Exploitation
Not listed in the CISA Known Exploited Vulnerabilities catalogue as of 2026.09.04. That is an absence of confirmed public exploitation, not evidence that exploitation has not occurred. EPSS models a 1.5% probability of exploitation activity in the next 30 days.
Affected products
| Product | Vendor | Type | Versions named |
|---|---|---|---|
| VS960HD | Synology | unknown | < 2.2.3-1505, < 2.3.6-1720 |
References
Vendor advisory and patch
- https://www.synology.com/security/advisory/Synology_SA_20_26
- https://www.synology.com/security/advisory/Synology_SA_20_26
- https://www.talosintelligence.com/vulnerability_reports/TALOS-2020-1160 exploit
- https://www.talosintelligence.com/vulnerability_reports/TALOS-2020-1160 exploit
Record assembled from NVD, CISA KEV 2026.09.04 and FIRST EPSS 2026-09-04. Affected products are those NVD's CPE configuration names that fall inside this site's scope; a CVE may affect products outside it.