CVE-2021-27648Network attack vector

Authenticated privilege escalation via quarantine resource reference

Published Apr 28, 2021 · Updated Sep 16, 2024

Externally controlled resource reference in Synology Antivirus Essential before 1.4.8-2801 allows remote authenticated users to gain privileges. The quarantine functionality follows an externally controlled reference across a resource boundary, but Synology has not disclosed the exact locus or validation failure. Exploitation requires authenticated network access and user interaction; successful use grants elevated privileges with confidentiality, integrity, and availability impact.

CVSS severity9.0
Critical
EPSS probability2.84%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Externally controlled resource reference in Synology Antivirus Essential before 1.4.8-2801 allows remote authenticated users to gain privileges. The quarantine functionality follows an externally controlled reference across a resource boundary, but Synology has not disclosed the exact locus or validation failure. Exploitation requires authenticated network access and user interaction; successful use grants elevated privileges with confidentiality, integrity, and availability impact.

The record

CVE
CVE-2021-27648
Published
Apr 28, 2021
Updated
Sep 16, 2024
Vendor
Synology
Product
Synology Antivirus Essential
Classifications
CWE-610, T1068
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 28, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <1.4.8-2801

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Synology · Synology Antivirus Essentialversion=unspecified <1.4.8-2801

Published CVSS scores

9.0SynologyCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-610Externally Controlled Reference to a Resource in Another Sphere
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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