CVE-2024-21620: Junos OS: SRX Series and EX Series: J-Web doesn't sufficiently sanitize input to prevent XSS

Is it exploited?

Reported, not confirmed by CISA. VulnCheck KEV lists it as exploited in the wild. CISA has not added it to its Known Exploited Vulnerabilities catalog as of 29 Oct 2026.

VulnCheck KEV lists it since 24 Aug 2025. It cites 86 public reports, the first from 24 Aug 2025.

• dashboard.shadowserver.org
• dashboard.shadowserver.org
• dashboard.shadowserver.org

How likely is exploitation in the next 30 days?

0.9%

EPSS score, percentile 59.8 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?

8.8 High

CVSS v3.1 base score, given by the CNA

What should I do?

The following software releases have been updated to resolve this specific issue: 20.4R3-S10*, 21.2R3-S8*, 21.4R3-S6*, 22.1R3-S5*, 22.2R3-S3*, 22.3R3-S2*, 22.4R3-S1* … Full textSolution from the CVE record.

CISA has set no required action, because the vulnerability is not in KEV.

Advisories and patches (1)

Which versions are affected?

Affected

• before 20.4R3-S10
• from 21.2 to before 21.2R3-S8
• from 21.4 to before 21.4R3-S6
• from 22.1 to before 22.1R3-S5
• from 22.2 to before 22.2R3-S3
• from 22.3 to before 22.3R3-S2

and 3 more in the table below

Versions by product

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; VulnCheck KEV, as of 30 Oct 2026; FIRST EPSS, as of 29 Oct 2026; CVE List, as of 30 Oct 2026. About the data.

Description

Junos OS: SRX Series and EX Series: J-Web doesn't sufficiently sanitize input to prevent XSS

An Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in J-Web of Juniper Networks Junos OS on SRX Series and EX Series allows an attacker to construct a URL that when visited by another user enables the attacker to execute commands with the target's permissions, including an administrator. A specific invocation of the emit_debug_note method in webauth_operation.php will echo back the data it receives. This issue affects Juniper Networks Junos OS on SRX Series and EX Series: * All versions earlier than 20.4R3-S10; * 21.2 versions earlier than 21.2R3-S8; * 21.4 versions earlier than 21.4R3-S6; * 22.1 versions earlier than 22.1R3-S5; * 22.2 versions earlier than 22.2R3-S3; * 22.3 versions earlier than 22.3R3-S2; * 22.4 versions earlier than 22.4R3-S1; * 23.2 versions earlier than 23.2R2; * 23.4 versions earlier than 23.4R2.

Source: CVE List, as of 30 Oct 2026. About the data.

What to do

Advisories and patches

• supportportal.juniper.net (Vendor advisory)

Solution (from the CVE record)

The following software releases have been updated to resolve this specific issue: 20.4R3-S10*, 21.2R3-S8*, 21.4R3-S6*, 22.1R3-S5*, 22.2R3-S3*, 22.3R3-S2*, 22.4R3-S1*, 23.2R2*, 23.4R2*, 24.2R1*, and all subsequent releases. * Pending Publication

Workaround (from the CVE record)

Disable J-Web, or limit access to only trusted hosts and users.

This summary is based on the CVE record as of 30 Oct 2026. Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

Source: CVE List, as of 30 Oct 2026. About the data.

Timeline

Known exploited Juniper vulnerabilities

• CVE-2015-7755: Juniper ScreenOS Improper Authentication Vulnerability (added 2 Oct 2025)
• CVE-2025-21590: Juniper Junos OS Improper Isolation or Compartmentalization Vulnerability (added 13 Mar 2025)
• CVE-2023-36844: Juniper Junos OS EX Series PHP External Variable Modification Vulnerability (added 13 Nov 2023)
• CVE-2023-36845: Juniper Junos OS EX Series and SRX Series PHP External Variable Modification Vulnerability (added 13 Nov 2023)
• CVE-2023-36846: Juniper Junos OS SRX Series Missing Authentication for Critical Function Vulnerability (added 13 Nov 2023)