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Fencer Intel
critical 9.1

CVE-2021-4406 json

Authenticated Remote COmmand Execution as root in OSNEXUS QuantaStor version 6.0.0.355 and others

published 3y ago modified 4mo ago also EUVD-2021-34233

cvss
9.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.0%
EPSS 1.0% chance of exploitation in 30 days, percentile 61%
public exploits
0
none known

Summary

An authenticated attacker is able to create alerts that trigger a stored XSS attack.

POC

* go to the alert manager

* open the ITSM tab * add a webhook with the URL/service token value

' -h && id | tee /tmp/ttttttddddssss #' (whitespaces are tab characters)

* click add

* click apply

* create a test alert

* The test alert will run the command

“id | tee /tmp/ttttttddddssss” as root.

* after the test alert inspect

/tmp/ttttttddddssss it'll contain the ids of the root user.

Patch / fix

  • osnexus quantastor 6.0.0.355

Is CVE-2021-4406 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
total
Assessed
last yr.

Exploit prediction

0.96% chance of exploitation in the next 30 days, higher than 61% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • csirt.divd.nl https://csirt.divd.nl/CVE-2021-4406 referenced PoC, tagged "exploit" by a source, unverified
  • csirt.divd.nl https://csirt.divd.nl/cves/CVE-2021-4406/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
NVD 3.1 7.2 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Affected products

  • OSNEXUS QuantaStor

Classification

Weakness
  • CWE-77 Improper Neutralization of Special Elements used in a Command

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.