CVE-2026-21904 Junos Space: ilpFilter field on nLegacy.jsp is vulnerable to reflected cross-site script injection

What is CVE-2026-21904?

CVE-2026-21904 is a medium-severity cross-site scripting vulnerability in Juniper Junos Space, published on 9 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

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.

Weakness: CWE-79

Which versions are affected by CVE-2026-21904?

It affects 1 product.

Products include Juniper Junos Space.

How do I fix CVE-2026-21904?

No fix has been published for CVE-2026-21904 yet. Limit exposure of the affected software until one is available.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2026-21904 being exploited?

There is no known exploitation of CVE-2026-21904 in the wild and no public exploit code.

Other vulnerabilities in Juniper Junos Space

• CVE-2014-3412 Command injection in n/a Critical 10.0
• CVE-2014-3413 Hardcoded credentials in n/a Critical 9.8
• CVE-2016-1265 Junos Space: privilege escalation vulnerabilities in Junos Space Critical 9.8
• CVE-2017-10622 Junos Space: Authentication bypass vulnerability Critical 9.8
• CVE-2016-4926 Auth bypass in n/a Critical 9.8

All Juniper Junos Space vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-3cpj-89qh-f3x6.