CVE-2021-26565
Synology
- Published
- 26 February 2021
- Last modified
- 17 June 2026
- CVSS
- 5.9 v3.1
- Severity
- medium
- EPSS
- 0.7% (52th pct)
- CISA KEV
- Not listed
- NVD status
- Modified
- Weaknesses
- CWE-319
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Description
Cleartext transmission of sensitive information vulnerability in synorelayd in Synology DiskStation Manager (DSM) before 6.2.3-25426-3 allows man-in-the-middle attackers to obtain sensitive information via an HTTP session.
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 0.7% 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.