CVE-2021-26564
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 spoof servers via an HTTP session.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.67%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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 spoof servers via an HTTP session.
- CVSS 3.1
- 8.7 HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
- EPSS
- 0.67% probability · 52th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-319
- Affected
- synology/diskstation manager · synology/vs960hd firmware · synology/skynas firmware · synology/diskstation manager unified controller
- Source
- security@synology.com
EPSS 0.7% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://www.synology.com/security/advisory/Synology_SA_20_26Vendor Advisory
- https://www.talosintelligence.com/vulnerability_reports/TALOS-2020-1160Exploit, Third Party Advisory
- https://www.synology.com/security/advisory/Synology_SA_20_26Vendor Advisory
- https://www.talosintelligence.com/vulnerability_reports/TALOS-2020-1160Exploit, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.