CVE-2026-21904: An Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in Junip

Routine

MEDIUM 6.1DOWNGRADE

CVE-2026-21904 is a medium-severity flaw (CVSS 6.1) affecting junos space. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in Juniper Networks Junos Space allows an attacker to inject script tags in the list filter field that, when visited by another user, enables the attacker to execute commands with the target's permissions, including an administrator. This issue affects all versions of Junos Space before 24.1R5 Patch V3.

Why this priority

No elevated risk signals yet

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

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.2% (top 89%)
CISA exploited list	No
Weakness	CWE-79
Published	2026-04-09
Last modified	2026-10-26

Publisher (CNA): Juniper Networks, Inc. · Vendor: juniper

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-09 22:16 UTCPublished CVE record published
2026-10-26 21:10 UTCUpdated Record last modified

juniper junos space DOWNGRADE

Affected: 1.0 · 1.1 · 1.2 · 1.3 · 1.4 · 2.0 · 11.1 · 11.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.0

1. Check installed version

apt-cache policy junos-space || rpm -q junos-space || junos-space --version

2. No fixed release: DOWNGRADE to a release before 1.0 (Debian / Ubuntu)

apt-cache madison junos-space sudo apt install junos-space=<VERSION_BEFORE_1.0> sudo apt-mark hold junos-space

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

dnf --showduplicates list junos-space sudo dnf downgrade junos-space-<VERSION_BEFORE_1.0> sudo dnf versionlock add junos-space

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-2026-21904?

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

Is CVE-2026-21904 being exploited?

CVE-2026-21904 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-2026-21904 affect?

CVE-2026-21904 affects junos space. Severity is medium (CVSS 6.1). An Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in Juniper Networks Junos Space allows an attacker to inject script tags in the list filter field that, when visited by another user, en

How urgent is CVE-2026-21904?

Priority 24/100. No elevated risk signals yet.

Software pages

Juniper Junos vulnerabilities

References

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