CVE-2025-57539Public exploitNetwork attack vector

Administrator-stored XSS via unneutralized configuration fields

Published Sep 9, 2025 · Updated Sep 9, 2025

Stored XSS in Proxmox Virtual Environment 8.4 allows remote authenticated users to execute JavaScript in another user's browser. The Web UI stores unneutralized HTML from the HTTP Proxy, WebAuthn Relying Party, and U2F Origin configuration fields and renders it when another user opens those settings. Writing these values requires Sys.Modify on /, a privilege assigned only to the Administrator role by default, and viewing the poisoned settings triggers execution in the victim's session.

CVSS severity5.4
Medium
EPSS probability0.29%
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 Proxmox Virtual Environment 8.4 allows remote authenticated users to execute JavaScript in another user's browser. The Web UI stores unneutralized HTML from the HTTP Proxy, WebAuthn Relying Party, and U2F Origin configuration fields and renders it when another user opens those settings. Writing these values requires Sys.Modify on /, a privilege assigned only to the Administrator role by default, and viewing the poisoned settings triggers execution in the victim's session.

The record

CVE
CVE-2025-57539
Published
Sep 9, 2025
Updated
Sep 9, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Sep 9, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 9, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.4CISA-ADPCVSS:3.1/AV:N/AC:L/PR:L/UI:R/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.

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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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007Command and Scripting Interpreter: JavaScript

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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