CVE-2021-27649Network attack vector

Unauthenticated code execution via file-transfer use-after-free

Published Jun 23, 2021 · Updated Sep 16, 2024

Use-after-free in Synology DiskStation Manager before 6.2.3-25426-3 allows remote attackers to execute arbitrary code over the network. Synology identifies the locus only as the file transfer protocol component and has not published the freed object's lifetime or triggering input. No authentication or user interaction is required; the published record does not identify the affected protocol or the privileges of executed code.

CVSS severity9.8
Critical
EPSS probability2.01%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Synology DiskStation Manager before 6.2.3-25426-3 allows remote attackers to execute arbitrary code over the network. Synology identifies the locus only as the file transfer protocol component and has not published the freed object's lifetime or triggering input. No authentication or user interaction is required; the published record does not identify the affected protocol or the privileges of executed code.

The record

CVE
CVE-2021-27649
Published
Jun 23, 2021
Updated
Sep 16, 2024
Vendor
Synology
Product
DiskStation Manager
Classifications
CWE-416, T1210
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 23, 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 <6.2.3-25426-3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Synology · DiskStation Managerversion=unspecified <6.2.3-25426-3

Published CVSS scores

7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8Synology Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
T1210Exploitation of Remote Services

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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