What’s Vulnerable › Vulnerabilities

CVE-2021-26561

• Severity: high (CVSS 8.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.1% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-02-26 · updated 2026-06-17
• Weakness: CWE-121

Description

Stack-based buffer overflow vulnerability in synoagentregisterd in Synology DiskStation Manager (DSM) before 6.2.3-25426-3 allows man-in-the-middle attackers to execute arbitrary code via syno_finder_site HTTP header.

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-2020-1159
• https://www.synology.com/security/advisory/Synology_SA_20_26
• https://www.talosintelligence.com/vulnerability_reports/TALOS-2020-1159

Get alerted when CVE-2021-26561 or the next vulnerability affects your stack