CVE-2026-61399: Improper Encoding or Escaping of Output vulnerability in Apache CloudStack's UI while using Lock User Function

Routine

MEDIUM 4.8WATCHLISTUPGRADE

CVE-2026-61399 is a medium-severity flaw (CVSS 4.8) affecting cloudstack. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Improper Encoding or Escaping of Output vulnerability in Apache CloudStack's UI while using Lock User Functionality. This issue affects Apache CloudStack: from 4.20.0.0 through 4.20.3.0 and from 4.21.0.0 through 4.22.1.0. Users are recommended to upgrade to version 4.20.3.1 or 4.22.1.1 or later, which fixes the issue.

Why this priority

On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	4.8 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	High
User interaction	Required
EPSS exploit chance	0.5% (top 57%)
CISA exploited list	No
Weakness	CWE-116
Published	2026-08-21
Last modified	2026-10-16

Publisher (CNA): Apache Software Foundation · Vendor: apache

Last updated 2026-10-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-21 09:16 UTCPublished CVE record published
2026-10-16 15:10 UTCUpdated Record last modified

apache cloudstack UPGRADE

Affected: >= 4.20.0.0 and < 4.20.3.1 · >= 4.21.0.0 and < 4.22.1.1

Fixed in: 4.20.3.1, 4.22.1.1

Safe to downgrade to: a release before 4.20.0.0

1. Check installed version

apt-cache policy cloudstack || rpm -q cloudstack || cloudstack --version

2. UPGRADE to 4.20.3.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade cloudstack

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade cloudstack

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 4.20.0.0 (Debian / Ubuntu)

apt-cache madison cloudstack sudo apt install cloudstack=<VERSION_BEFORE_4.20.0.0> sudo apt-mark hold cloudstack

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list cloudstack sudo dnf downgrade cloudstack-<VERSION_BEFORE_4.20.0.0> sudo dnf versionlock add cloudstack

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-2026-61399?

cloudstack: upgrade to 4.20.3.1, 4.22.1.1. Exact commands for each OS are on this page.

Is CVE-2026-61399 being exploited?

CVE-2026-61399 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-2026-61399 affect?

CVE-2026-61399 affects cloudstack. Severity is medium (CVSS 4.8). Improper Encoding or Escaping of Output vulnerability in Apache CloudStack's UI while using Lock User Functionality. This issue affects Apache CloudStack: from 4.20.0.0 through 4.20.3.0 and from 4.21.0.0 through 4.22.1.0. Users are recomm

How urgent is CVE-2026-61399?

Priority 32/100. On your watchlist

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References

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