What’s Vulnerable › Vulnerabilities

CVE-2021-26566

• Severity: critical (CVSS 9.0 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.5% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-02-26 · updated 2026-06-17
• Weakness: CWE-201

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.

Affected products

• Synology DiskStation Manager: before 6.2.3-25426-3 — fixed in 6.2.3-25426-3
• Synology Diskstation Manager Unified Controller: 3.0
• Synology Skynas Firmware: all versions
• Synology Vs960Hd Firmware: all versions

How to fix

Upgrade to a fixed version: Synology DiskStation Manager 6.2.3-25426-3. Check the vendor advisory for mitigations.

References

• https://www.synology.com/security/advisory/Synology_SA_20_26
• https://www.talosintelligence.com/vulnerability_reports/TALOS-2020-1160
• https://www.synology.com/security/advisory/Synology_SA_20_26
• https://www.talosintelligence.com/vulnerability_reports/TALOS-2020-1160

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