CVE-2026-34803Network attack vector

Authenticated stored XSS via unsanitized QoS class name

Published Apr 2, 2026 · Updated Apr 2, 2026

Stored XSS in Endian Firewall 3.3.25 and earlier allows remote authenticated users to execute JavaScript via a QoS class name. The /manage/qos/classes/ handler accepts the name parameter, persists it, and later renders it into the affected page without neutralizing executable markup. Authenticated access is required to submit the payload, and another user must view the page; execution is limited to that viewer's browser context.

CVSS severity5.1
Medium
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in Endian Firewall 3.3.25 and earlier allows remote authenticated users to execute JavaScript via a QoS class name. The /manage/qos/classes/ handler accepts the name parameter, persists it, and later renders it into the affected page without neutralizing executable markup. Authenticated access is required to submit the payload, and another user must view the page; execution is limited to that viewer's browser context.

The record

CVE
CVE-2026-34803
Published
Apr 2, 2026
Updated
Apr 2, 2026
Vendor
Endian
Product
Endian Firewall
Classifications
CWE-79, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 2, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 2, 2026Record 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=3.3.25

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Endian · Endian Firewallversion=3.3.25

Published CVSS scores

5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
5.1VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
6.4VulnCheckCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

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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