CVE-2022-20678
📋 TL;DR
This vulnerability allows unauthenticated remote attackers to cause Cisco IOS XE devices with AppNav-XE feature enabled to reload, resulting in denial of service. Attackers can exploit it by sending crafted TCP traffic at high rates through interfaces with AppNav interception enabled. Only devices running affected Cisco IOS XE software versions with AppNav-XE configured are vulnerable.
💻 Affected Systems
- Cisco IOS XE Software
📦 What is this software?
Ios Xe by Cisco
Cisco IOS XE is Cisco's modern network operating system running on enterprise routers, switches, and wireless controllers deployed across corporate networks, data centers, branch offices, and service provider infrastructure worldwide. As the evolution of Cisco IOS, IOS XE provides a Linux-based modu...
Learn more about Ios Xe →Ios Xe by Cisco
Cisco IOS XE is Cisco's modern network operating system running on enterprise routers, switches, and wireless controllers deployed across corporate networks, data centers, branch offices, and service provider infrastructure worldwide. As the evolution of Cisco IOS, IOS XE provides a Linux-based modu...
Learn more about Ios Xe →Ios Xe by Cisco
Cisco IOS XE is Cisco's modern network operating system running on enterprise routers, switches, and wireless controllers deployed across corporate networks, data centers, branch offices, and service provider infrastructure worldwide. As the evolution of Cisco IOS, IOS XE provides a Linux-based modu...
Learn more about Ios Xe →Ios Xe by Cisco
Cisco IOS XE is Cisco's modern network operating system running on enterprise routers, switches, and wireless controllers deployed across corporate networks, data centers, branch offices, and service provider infrastructure worldwide. As the evolution of Cisco IOS, IOS XE provides a Linux-based modu...
Learn more about Ios Xe →⚠️ Risk & Real-World Impact
Worst Case
Complete device reload causing extended service disruption, potential cascading network failures, and loss of critical network services.
Likely Case
Intermittent device reloads causing service interruptions, degraded network performance, and increased operational overhead.
If Mitigated
No impact if AppNav-XE is disabled or devices are patched/isolated from untrusted traffic.
🎯 Exploit Status
Exploitation requires sending crafted TCP traffic at high rates through vulnerable interfaces. No authentication required.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Cisco IOS XE Software releases 17.9.1, 17.10.1, 17.11.1 and later
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-appnav-xe-dos-j5MXTR4
Restart Required: Yes
Instructions:
1. Check current IOS XE version with 'show version'. 2. Download appropriate fixed release from Cisco Software Center. 3. Follow Cisco IOS XE upgrade procedures. 4. Reload device after upgrade.
🔧 Temporary Workarounds
Disable AppNav-XE feature
allRemove AppNav configuration from interfaces to eliminate vulnerability
no service-policy type appnav input [policy-name]
no service-policy type appnav output [policy-name]
Apply ACL restrictions
allRestrict TCP traffic to AppNav-enabled interfaces from trusted sources only
access-list [acl-number] permit tcp [trusted-source] any
interface [interface-name]
ip access-group [acl-number] in
🧯 If You Can't Patch
- Disable AppNav-XE feature on all interfaces immediately
- Implement strict network segmentation and ACLs to restrict traffic to AppNav-enabled interfaces
🔍 How to Verify
Check if Vulnerable:
Check if AppNav is configured: 'show running-config | include appnav' and check IOS XE version: 'show version | include Version'Check Version:
show version | include VersionVerify Fix Applied:
Verify upgraded to fixed version: 'show version | include 17.9.1|17.10.1|17.11.1' and confirm AppNav configuration if still needed📡 Detection & Monitoring
Log Indicators:
- Unexpected device reloads
- AppNav process crashes
- High CPU utilization on AppNav processes
- TCP traffic anomalies on AppNav interfaces
Network Indicators:
- High rate TCP traffic to AppNav-enabled interfaces
- Unusual TCP flag combinations
- Device unreachability patterns
SIEM Query:
source="cisco-ios" (reload OR crash OR "%SYS-5-RESTART") AND (appnav OR AppNav)