CVE-2024-39553
📋 TL;DR
An unauthenticated network attacker can crash the msvcsd process on Juniper Junos OS Evolved devices configured with inline jflow, causing temporary denial of service and potential unauthorized access. This affects multiple Junos OS Evolved versions and requires inline jflow configuration. The service automatically recovers after crashing.
💻 Affected Systems
- Juniper Networks Junos OS Evolved
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Repeated exploitation could cause sustained service disruption, potentially allowing unauthorized network access and impacting system integrity.
Likely Case
Temporary denial of service as the msvcsd process crashes and automatically recovers, with no impact to forwarding traffic.
If Mitigated
Limited to temporary service disruption with automatic recovery if proper network segmentation and access controls are implemented.
🎯 Exploit Status
Unauthenticated network-based attack requiring inline jflow configuration. No public exploit code known at this time.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 21.4R3-S7-EVO, 22.2R3-S3-EVO, 22.3R3-S2-EVO, 22.4R3-EVO, 23.2R1-S2-EVO, 23.2R2-EVO or later
Vendor Advisory: https://supportportal.juniper.net/JSA79101
Restart Required: Yes
Instructions:
1. Download appropriate patched version from Juniper support portal. 2. Backup current configuration. 3. Install update following Juniper upgrade procedures. 4. Reboot device to apply changes.
🔧 Temporary Workarounds
Disable inline jflow
allRemove or disable inline jflow configuration to eliminate vulnerability
configure
delete services flow-monitoring version9 inline-jflow
commit
Network segmentation
allRestrict network access to devices with inline jflow configuration
🧯 If You Can't Patch
- Disable inline jflow configuration immediately
- Implement strict network access controls to limit exposure to trusted sources only
🔍 How to Verify
Check if Vulnerable:
Check if inline jflow is configured: 'show configuration services flow-monitoring version9 inline-jflow' and verify OS version is in affected rangeCheck Version:
show versionVerify Fix Applied:
Verify OS version is patched: 'show version' and confirm inline jflow configuration status📡 Detection & Monitoring
Log Indicators:
- msvcsd process crashes
- service restart messages
- unexpected sampling service failures
Network Indicators:
- Unexpected traffic to sampling service ports
- Pattern of service disruption
SIEM Query:
source="juniper-firewall" AND (process="msvcsd" AND event="crash") OR (service="sampling" AND status="failed")