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Vulnerability record · CVE-2021-26566 · published 26 February 2021

CVE-2021-26566: Synology diskstation manager information exposure vulnerability

Synology · Diskstation Manager

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.

9.0 CVSS 3.1 Critical EPSS 1.5% · top 26.5% CWE-201 · CWE-201CWE-200 · Information exposure
9.0CVSS 3.1 base score, v2 6.8
1.5%EPSS exploitation probability, 30 days
NoNot in CISA KEV
4Affected product versions listed by NVD
4References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

Affected products

4 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://www.synology.com/security/advisory/Synology_SA_20_26 Vendor Advisory
https://www.talosintelligence.com/vulnerability_reports/TALOS-2020-1160 ExploitThird Party Advisory
https://www.synology.com/security/advisory/Synology_SA_20_26 Vendor Advisory
https://www.talosintelligence.com/vulnerability_reports/TALOS-2020-1160 ExploitThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

7.8CVE-2021-3156Sudo off-by-one heap overflow allows root privilege escalationSudo before 1.9.5p2 contains an off-by-one error leading to a heap-based buffer overflow. Triggering it via 'sudoedit -s' with a command-line argumen…KEVEPSS 100%analysed10.0CVE-2013-6955Synology DSM imageSelector.cgi arbitrary file append and code executionSynology DiskStation Manager (DSM) versions 4.0 before 4.0-2259, 4.2 before 4.2-3243, and 4.3 before 4.3-3810 Update 1 contain a flaw in webman/image…EPSS 85%analysed9.8CVE-2025-13392Synology diskstation manager vulnerabilityImproper check for unusual or exceptional conditions vulnerability in SSO in Synology DiskStation Manager (DSM) before 7.2.2-72806-5 and 7.3.1-86003-…EPSS 0.53%9.8CVE-2024-10441Synology beestation os vulnerabilityImproper encoding or escaping of output vulnerability in the system plugin daemon in Synology BeeStation OS (BSM) before 1.1-65374 and Synology DiskS…EPSS 1.2%9.8CVE-2022-27625Synology diskstation manager memory buffer overflow vulnerabilityA vulnerability regarding improper restriction of operations within the bounds of a memory buffer is found in the message processing functionality of…EPSS 1.6%9.8CVE-2022-27624Synology diskstation manager memory buffer overflow vulnerabilityA vulnerability regarding improper restriction of operations within the bounds of a memory buffer is found in the packet decryption functionality of …EPSS 1.6%9.8CVE-2022-22687Synology diskstation manager classic buffer overflow vulnerabilityBuffer copy without checking size of input ('Classic Buffer Overflow') vulnerability in Authentication functionality in Synology DiskStation Manager …EPSS 2.4%9.8CVE-2021-43926Synology diskstation manager sql injection vulnerabilityImproper neutralization of special elements used in an SQL command ('SQL Injection') vulnerability in Log Management functionality in Synology DiskSt…EPSS 0.88%

Source: NIST National Vulnerability Database (record CVE-2021-26566), CISA KEV, FIRST EPSS (scores of 2026-10-03). This page is refreshed as NVD updates the record.