MEDIUM CVSS 4.4
Published: 2025-03-12

CVE-2025-21590

juniper junos Security Advisory (CVE-2025-21590)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2025-21590 impacting juniper junos. Evaluated with CVSS Base Score of 4.4 (MEDIUM).

Original NVD Description

Source: NIST NVD
An Improper Isolation or Compartmentalization vulnerability in the kernel of Juniper Networks Junos OS allows a local attacker with high privileges to compromise the integrity of the device. A local attacker with access to the shell is able to inject arbitrary code which can compromise an affected device. This issue is not exploitable from the Junos CLI. This issue affects Junos OS:  * All versions before 21.2R3-S9, * 21.4 versions before 21.4R3-S10,  * 22.2 versions before 22.2R3-S6,  * 22.4 versions before 22.4R3-S6,  * 23.2 versions before 23.2R2-S3,  * 23.4 versions before 23.4R2-S4, * 24.2 versions before 24.2R1-S2, 24.2R2.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Local (AV:L)
Requires local system execution permissions
Attack Complexity
Low (AC:L)
No specialized conditions required
Privileges Required
High (PR:H)
Administrative credentials required
User Interaction
None (UI:N)
Zero human interaction required
Scope
Unchanged (S:U)
Confined to same security context
Confidentiality
None (C:N)
No data confidentiality impact
Integrity
High (I:H)
Total modification of target system
Availability
None (A:N)
No system availability impact

🎯 Affected Versions Matrix

Affected Product juniper / junos
Affected Versions *
Weakness Enumeration CWE-653

Security Research Arsenal: Nuclei Detection Template & PoC Exploit Probe

High-Intent Research Tool

Ready-to-use security scanner signatures, active verification probe skeletons, and remediation playbooks for CVE-2025-21590 impacting juniper junos.

⚡ Nuclei Detection Template (YAML) cve-2025-21590.yaml
id: cve-2025-21590

info:
  name: juniper junos - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: medium
  description: |
    Automated signature & scanner for CVE-2025-21590 affecting juniper junos.
    Evaluation: An Improper Isolation or Compartmentalization vulnerability in the kernel of Juniper Networks Junos OS allows a local attacker with high privileges to...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2025-21590
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N
    cvss-score: 4.4
    cve-id: CVE-2025-21590
    cwe-id: CWE-653
  tags: cve,cve-2025-21590,juniper,junos,medium

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "junos"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2025-21590.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2025-21590
# Target: juniper junos | CVSS: 4.4 (MEDIUM)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2025-21590 (juniper junos)...")
    headers = {
        "User-Agent": "CyberVault-Audit-Scanner/2.0",
        "Accept": "*/*"
    }
    try:
        r = requests.get(f"{target_url.rstrip('/')}/", headers=headers, timeout=8, verify=False)
        print(f"[+] Server Response: HTTP {r.status_code} | Server Banner: {r.headers.get('Server', 'Unknown')}")
        if r.status_code < 500:
            print(f"[!] Target reachable. Verify version against juniper junos scope (*).")
        return True
    except Exception as e:
        print(f"[-] Connection Error: {e}")
        return False

if __name__ == '__main__':
    url = sys.argv[1] if len(sys.argv) > 1 else "http://localhost:8080"
    verify_vulnerability(url)
🛡️ Quick Patch & Remediation Script (Bash) patch_cve-2025-21590.sh
# Recommended Remediation & Patching Commands for CVE-2025-21590
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install junos 2>/dev/null || \
sudo dnf upgrade junos 2>/dev/null || \
sudo yum update junos

# 2. Inspect installed package versions for vulnerable scope:
dpkg -l | grep -i junos 2>/dev/null || rpm -qa | grep -i junos

# 3. Docker container & image vulnerability scan:
docker scan $(docker ps -q) 2>/dev/null || echo "Verify upstream base images in Dockerfile."

🛡️ Remediation & Security Action

  • Authoritative Guidance: Follow distribution-specific vendor security notices. Advisory status and package patches vary by distribution release.
  • Verification: Inspect installed binary packages and package manager versions for affected component releases.
  • Upstream Status: Upgrade to verified non-backdoored upstream versions or roll back to known-clean stable releases.
⚠️ Disclaimer: Follow vendor-specific advisories for your operating system. CyberVault does not fabricate unsupported remediation scripts.

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2025-21590 in juniper junos?

Review vendor-specific security notices and update juniper junos packages to the latest patched release immediately. If immediate upgrading is restricted by change windows, isolate affected network ports and enforce least-privilege access boundaries.

Is there an active exploit or public PoC for CVE-2025-21590?

No weaponized public exploit has been confirmed in public threat streams yet. Continuous surveillance is active across GitHub and security feeds.

What is the CVSS 3.1 severity rating and impact for CVE-2025-21590?

CVE-2025-21590 is classified with a CVSS 3.1 Base Score of 4.4 (MEDIUM). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
4.4
MEDIUM SEVERITY
CVE ID CVE-2025-21590
Weakness CWE-653
Vendor juniper
Product junos
Published 2025-03-12
Vector CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N