Public proof of conceptFix available

CVE-2021-3310

Q: Is CVE-2021-3310 actively exploited?

Active exploitation of CVE-2021-3310 has not been confirmed. Its EPSS score was 1.0% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-3310?

CVE-2021-3310 has a CVSS v3 base score of 7.8 (HIGH severity), with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

A public proof of concept exists; no exploitation attested.

Published2021-03-10
Fixed in5.10.122
WeaknessCWE-59

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Western Digital My Cloud OS 5 devices before 5.10.122 mishandle Symbolic Link Following on SMB and AFP shares. This can lead to code execution and information disclosure (by reading local files).

Timeline

dates in UTC

2021-03-1005:15CVE publishedNVD
2026-10-2319:23First public proof of conceptPoC-in-GitHub

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-3310?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-3310?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Westerndigital my cloud osversion to verify

Branch	Affected	Fixed in	Source
5.10	< 5.10.122	5.10.122	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update Westerndigital my cloud os to 5.10.122

Advisories and patches

www.westerndigital.comVendor Advisory

Detection

read 2026-10-23 19:23 UTC

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: 1 repository, unverifiedpiffd0s/CVE-2021-3310

Sources

NVDCVSS 3.17.8read 2026-10-23
NVDCVSS 2.04.6read 2026-10-23
NVDweakness (CWE)CWE-59read 2026-10-23
FIRST EPSSEPSS score1.0 %2026-10-22
PoC-in-GitHubproof of concept1read 2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Published: 2021-03-10
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-3310?

Western Digital My Cloud OS 5 devices before 5.10.122 mishandle Symbolic Link Following on SMB and AFP shares. This can lead to code execution and information disclosure (by reading local files).

Is CVE-2021-3310 actively exploited?

Active exploitation of CVE-2021-3310 has not been confirmed. Its EPSS score was 1.0% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-3310?

CVE-2021-3310 has a CVSS v3 base score of 7.8 (HIGH severity), with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

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