CVE-2021-34811Network attack vector

Intranet resource access via server-side request forgery

Published Jun 18, 2021 · Updated Sep 16, 2024

Server-side request forgery in Synology Download Station before 3.8.16-3566 allows remote authenticated users to access intranet resources. The task-management component uses an unspecified attacker-controlled task input to issue a server-side request; Synology has not disclosed the affected endpoint or validation failure. An authenticated Download Station session is required, and the documented consequence is limited to reaching intranet resources.

CVSS severity5.0
Medium
EPSS probability0.76%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Server-side request forgery in Synology Download Station before 3.8.16-3566 allows remote authenticated users to access intranet resources. The task-management component uses an unspecified attacker-controlled task input to issue a server-side request; Synology has not disclosed the affected endpoint or validation failure. An authenticated Download Station session is required, and the documented consequence is limited to reaching intranet resources.

The record

CVE
CVE-2021-34811
Published
Jun 18, 2021
Updated
Sep 16, 2024
Vendor
Synology
Product
Download Station
Classifications
CWE-918, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 18, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=unspecified <3.8.16-3566

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Synology · Download Stationversion=unspecified <3.8.16-3566

Published CVSS scores

4.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
5.0Synology Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N
4.0NIST NVDAV:N/AC:L/Au:S/C:P/I:N/A:N

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-918Server-Side Request Forgery (SSRF)
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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo