CVE-2021-26564

Cleartext transmission of sensitive information vulnerability in synorelayd in Synology...

8.3 High

CVE-2021-26564 is a high vulnerability (CVSS 8.3) in Synology Diskstation Manager, published February 26, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.67%, the 51st percentile. No source names a fixed version.

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.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: High
Privileges needed: None
User interaction: Required

What an attacker can affect

Confidentiality: High
Integrity: High
Availability: High

Exploit likelihood

0.67%Up 0.3 points since Apr 14, 2021

What each source reports

CVE List Score used 8.3

Record: CVE-2021-26564
CVSS 3.1: 8.3 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H
Weakness: CWE-319
Updated: 2026-11-02

EUVDEUVD-2021-13362 8.3

Record: EUVD-2021-13362
CVSS 3.1: 8.3 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H
Updated: 2026-11-03

GitHub AdvisoriesGHSA-77r2-rjfh-m7wh 8.7

Cleartext transmission of sensitive information vulnerability in synorelayd in Synology...

Record: GHSA-77r2-rjfh-m7wh
CVSS 3.1: 8.7 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
Weakness: CWE-319
Updated: 2026-11-02

NVD 8.3

Record: CVE-2021-26564
CVSS 3.1: 8.3 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H
CVSS 3.1: 8.7 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
CVSS 2.0: 5.8 MediumAV:N/AC:M/Au:N/C:P/I:P/A:N
Weakness: CWE-319
Updated: 2026-11-02

Affected products

History

History
When	Changed	Sources
2026-11-03	aliases, published	EUVD
2026-11-02	created	CVE List, GitHub Advisories, NVD