CVE-2021-27646Network attack vector

Remote code execution via iscsi use after free

Published Mar 12, 2021 · Updated Sep 16, 2024

Use-after-free in iscsi_snapshot_comm_core in Synology DiskStation Manager before 6.2.3-25426-3 allows remote attackers to execute arbitrary code via crafted web requests. The service lacks proper locking while operating on an object, allowing a pointer to be reused after the object is freed. No authentication or user interaction is required, so a network attacker can send crafted requests and execute code in the service process, affecting confidentiality, integrity, and availability.

CVSS severity9.8
Critical
EPSS probability3.79%
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 iscsi_snapshot_comm_core in Synology DiskStation Manager before 6.2.3-25426-3 allows remote attackers to execute arbitrary code via crafted web requests. The service lacks proper locking while operating on an object, allowing a pointer to be reused after the object is freed. No authentication or user interaction is required, so a network attacker can send crafted requests and execute code in the service process, affecting confidentiality, integrity, and availability.

The record

CVE
CVE-2021-27646
Published
Mar 12, 2021
Updated
Sep 16, 2024
Vendor
Synology
Product
Synology DiskStation Manager
Classifications
CWE-416, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 12, 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 · Synology DiskStation Managerversion=unspecified <6.2.3-25426-3

Published CVSS scores

9.8Synology Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NVDAV:N/AC:L/Au:N/C:P/I:P/A:P

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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
T1190Exploit Public-Facing Application

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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