CVE-2025-57540: A stored cross-site scripting (XSS) vulnerability exists in the WebAuthn Relying Party field within the Datace

Routine

MEDIUM 5.4DOWNGRADE

CVE-2025-57540 is a medium-severity flaw (CVSS 5.4) affecting virtual environment. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A stored cross-site scripting (XSS) vulnerability exists in the WebAuthn Relying Party field within the Datacenter configuration of Proxmox Virtual Environment (PVE) 8.4. Authenticated users can inject JavaScript code that is later executed in the browsers of users who view the configuration page, enabling client-side attacks.

Why this priority

Public exploit reference

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	5.4 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.3% (top 78%)
CISA exploited list	No
Weakness	CWE-79
Published	2025-09-09
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: proxmox

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-09-09 17:16 UTCPublished CVE record published
2026-06-17 09:43 UTCUpdated Record last modified

proxmox virtual environment DOWNGRADE

Affected: 8.4

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.4

1. Check installed version

apt-cache policy virtual-environment || rpm -q virtual-environment || virtual-environment --version

2. No fixed release: DOWNGRADE to a release before 8.4 (Debian / Ubuntu)

apt-cache madison virtual-environment sudo apt install virtual-environment=<VERSION_BEFORE_8.4> sudo apt-mark hold virtual-environment

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list virtual-environment sudo dnf downgrade virtual-environment-<VERSION_BEFORE_8.4> sudo dnf versionlock add virtual-environment

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2025-57540?

virtual environment: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2025-57540 being exploited?

CVE-2025-57540 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2025-57540 affect?

CVE-2025-57540 affects virtual environment. Severity is medium (CVSS 5.4). A stored cross-site scripting (XSS) vulnerability exists in the WebAuthn Relying Party field within the Datacenter configuration of Proxmox Virtual Environment (PVE) 8.4. Authenticated users can inject JavaScript code that is later executed

How urgent is CVE-2025-57540?

Priority 29/100. Public exploit reference

Software pages

Proxmox vulnerabilities

Related CVEs

CVE-2025-57539 MEDIUM 5.4 DOWNGRADE A stored cross-site scripting (XSS) vulnerability in the U2F Origin field of the Datacenter configuration in P
CVE-2025-57538 MEDIUM 5.4 DOWNGRADE A stored cross-site scripting (XSS) vulnerability in the HTTP Proxy field within the Datacenter configuration

References

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