CVE-2021-29087Network attack vector

Arbitrary file write via webapi path traversal

Published Jun 23, 2021 · Updated Sep 16, 2024

Path traversal in the webapi component in Synology DiskStation Manager before 6.2.3-25426-3 allows remote attackers to write arbitrary files. Synology identifies improper pathname restriction in webapi but has not published the affected endpoint, parameter, or normalization error. No authentication or user interaction is required; the documented consequence is an integrity-only arbitrary file write, with no reported file read or service interruption.

CVSS severity7.5
High
EPSS probability1.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path traversal in the webapi component in Synology DiskStation Manager before 6.2.3-25426-3 allows remote attackers to write arbitrary files. Synology identifies improper pathname restriction in webapi but has not published the affected endpoint, parameter, or normalization error. No authentication or user interaction is required; the documented consequence is an integrity-only arbitrary file write, with no reported file read or service interruption.

The record

CVE
CVE-2021-29087
Published
Jun 23, 2021
Updated
Sep 16, 2024
Vendor
Synology
Product
DiskStation Manager
Classifications
CWE-22
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

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:N
7.5Synology Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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