CVE-2021-3310Public exploitNetwork attack vector

Unauthenticated file disclosure via share symlink following

Published Mar 10, 2021 · Updated Aug 3, 2024

Link following in Western Digital Cloud OS 5 before 5.10.122 allows remote attackers to read arbitrary files through SMB or AFP shares. The SMB and AFP services accept attacker-created symbolic links and resolve them beyond the share root, exposing files accessible to the service account. An exposed share is sufficient and requires no authentication; leaked session tokens can support a larger chain, but direct access remains service-account scoped.

CVSS severity7.8
High
EPSS probability1.01%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Link following in Western Digital Cloud OS 5 before 5.10.122 allows remote attackers to read arbitrary files through SMB or AFP shares. The SMB and AFP services accept attacker-created symbolic links and resolve them beyond the share root, exposing files accessible to the service account. An exposed share is sufficient and requires no authentication; leaked session tokens can support a larger chain, but direct access remains service-account scoped.

The record

CVE
CVE-2021-3310
Published
Mar 10, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-59, T1005
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 10, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
4.6NIST NVDAV:L/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 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 exploitPublished

Weakness, pattern, technique

CWE-59Improper Link Resolution Before File Access ('Link Following')
T1005Data from Local System

Public exploit references

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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