CVE-2021-42080Public exploitNetwork attack vector

Browser script execution via unescaped echo input

Published Jul 10, 2023 · Updated Sep 22, 2025

Reflected XSS in OSNEXUS QuantaStor before 6.0.0.355 allows remote attackers to run script in a user's browser via a crafted URL. The unauthenticated qstorapi/echo endpoint places the inputMessage query value into its response without neutralizing HTML event-handler markup. Exploitation requires a user to open the URL; the demonstrated payload reads document.cookie in the QuantaStor origin, exposing browser-accessible session data.

CVSS severity7.4
High
EPSS probability0.69%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reflected XSS in OSNEXUS QuantaStor before 6.0.0.355 allows remote attackers to run script in a user's browser via a crafted URL. The unauthenticated qstorapi/echo endpoint places the inputMessage query value into its response without neutralizing HTML event-handler markup. Exploitation requires a user to open the URL; the demonstrated payload reads document.cookie in the QuantaStor origin, exposing browser-accessible session data.

The record

CVE
CVE-2021-42080
Published
Jul 10, 2023
Updated
Sep 22, 2025
Vendor
OSNEXUS
Product
QuantaStor
Classifications
CWE-79, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 10, 2023CVE publishedPublication date reported by the CVE source.
  2. Sep 22, 2025Record 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=0 <6.0.0.355

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OSNEXUS · QuantaStorversion=0 <6.0.0.355

Published CVSS scores

7.4Dutch Institute for Vulnerability DisclosureCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1189Drive-by Compromise

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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