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VulnerabilityPublished Updated

CVE-2024-21620: Juniper Networks Junos OS · Cross-site Scripting

Affects Juniper Networks Junos OSSource CVE Database V5

0

Not known to be exploited · CVSS 8.8 High.

Data as of 26 Oct 2026, 10:12 UTC

CVSS 3.1 base score
8.8High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.9% chance of exploitation in 30 days – higher than 59% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 25 Jan 2024

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
Juniper Networks Junos OSAffected
  • 0 – 23.4
9 affected builds
Fixed in–

AI-suggested

  1. Immediate patching: Organizations should prioritize upgrading Junos OS on affected SRX and EX Series devices to the fixed versions listed (e.g., 20.4R3-S10 or later). Applying vendor-provided patches is the most effective mitigation.
  2. Access restrictions: Limit access to the J-Web management interface to trusted networks and IP addresses only, using firewall rules and network segmentation to reduce exposure.
  3. Multi-factor authentication (MFA): Enforce MFA for administrative access to the management interface to reduce risk from compromised credentials.
  4. User awareness: Train network administrators to recognize and avoid phishing attempts that could deliver malicious URLs exploiting this vulnerability.
  5. Monitoring and logging: Enable detailed logging of management interface access and monitor for suspicious URL requests or unusual administrative activity.
  6. Disable J-Web if not required: If feasible, disable the web management interface and use CLI or other secure management methods to reduce attack surface.
  7. Incident response readiness: Prepare to respond to potential exploitation attempts by having forensic and recovery procedures in place for Juniper devices. These steps go beyond generic advice by focusing on reducing attack surface, enforcing strong access controls, and preparing for incident detection and response specific to Junos OS management interfaces.

Description

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.

References

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