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CVE-2021-26564

27
FAUCET Score

CVE-2021-26564 is a high-severity vulnerability affecting Synology DiskStation Manager (DSM) and related products, allowing cleartext transmission of sensitive information via synorelayd. This flaw enables man-in-the-middle attackers to spoof servers through HTTP sessions due to the absence of encryption. With a CVSS score of 8.7 (High), the vulnerability is remotely exploitable with high impact on confidentiality and integrity, but requires high attack complexity. There is currently no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 6.2.3-25426-3CPE matchmatch criteria
cpe:2.3:o:synology:diskstation_manager:*:*:*:*:*:*:*:*
Range not provided by sourceCPE matchmatch criteria
cpe:2.3:o:synology:vs960hd_firmware:-:*:*:*:*:*:*:*
Range not provided by sourceCPE matchmatch criteria
cpe:2.3:o:synology:skynas_firmware:-:*:*:*:*:*:*:*
3.0CPE matchmatch criteria
cpe:2.3:o:synology:diskstation_manager_unified_controller:3.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

8.3HIGH

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

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
1.6
Impact Score
6.0
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.65%
Probability of exploitation in next 30 days
EPSS Percentile
47.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0065 is in the 18th percentile among its peer group of 8,918 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

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