CVE-2026-21907
📋 TL;DR
This vulnerability allows attackers to decrypt TLS/SSL traffic by exploiting the use of static key ciphers in Juniper Junos Space servers. It affects all Junos Space versions before 24.1R5, compromising the confidentiality of network communications.
💻 Affected Systems
- Juniper Networks Junos Space
📦 What is this software?
Junos Space by Juniper
Junos Space by Juniper
Junos Space by Juniper
Junos Space by Juniper
Junos Space by Juniper
⚠️ Risk & Real-World Impact
Worst Case
Attackers with network access could decrypt all TLS/SSL traffic between Junos Space and clients, exposing sensitive management data and credentials.
Likely Case
On-path attackers could decrypt portions of encrypted traffic, potentially exposing administrative credentials and configuration data.
If Mitigated
With proper network segmentation and monitoring, impact is limited to potential exposure of non-critical management traffic.
🎯 Exploit Status
Exploitation requires network access to intercept traffic; no authentication needed for passive decryption attacks.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 24.1R5 or later
Vendor Advisory: https://kb.juniper.net/JSA106006
Restart Required: Yes
Instructions:
1. Backup Junos Space configuration. 2. Upgrade to Junos Space 24.1R5 or later. 3. Restart Junos Space services. 4. Verify TLS configuration no longer uses static key ciphers.
🔧 Temporary Workarounds
Disable static key ciphers
allManually disable ssl-static-key-ciphers in Junos Space TLS configuration
Configure via Junos Space web interface: Security > SSL/TLS Settings > Disable static key ciphers
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Junos Space from untrusted networks
- Deploy network monitoring and IDS/IPS to detect decryption attempts
🔍 How to Verify
Check if Vulnerable:
Check Junos Space version via web interface (Admin > System > About) or CLI: show versionCheck Version:
show versionVerify Fix Applied:
Verify version is 24.1R5 or later and check TLS configuration no longer lists static key ciphers📡 Detection & Monitoring
Log Indicators:
- Unusual TLS handshake patterns
- Multiple failed cipher negotiation attempts
Network Indicators:
- Network traffic showing use of static key ciphers (RC4, DES, etc.)
- SSL/TLS version downgrade attempts
SIEM Query:
tls.cipher_suite IN ("RC4", "DES", "3DES") AND dest_ip = [Junos Space IP]