CVE-2025-20159
📋 TL;DR
This vulnerability allows unauthenticated remote attackers to bypass management interface ACLs on affected Cisco IOS XR devices, potentially gaining unauthorized access via SSH, NetConf, or gRPC. It affects Cisco IOS XR Software on Packet I/O infrastructure platforms where ACLs are configured for these services.
💻 Affected Systems
- Cisco IOS XR Software
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
An attacker could bypass all management interface ACLs, gaining unauthorized administrative access to the device via SSH, NetConf, or gRPC, leading to full device compromise.
Likely Case
Attackers could bypass ACL restrictions to access management services that should be blocked, potentially probing or attacking the device if it is exposed.
If Mitigated
If ACLs are not relied upon as the sole control, and other security measures like network segmentation are in place, impact is limited to potential ACL bypass without further exploitation.
🎯 Exploit Status
Exploitation is straightforward as it involves sending traffic to bypass unsupported ACLs, but requires knowledge of the device's management interface.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Refer to Cisco advisory for fixed versions; typically requires upgrading to a patched release.
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-acl-packetio-Swjhhbtz
Restart Required: No
Instructions:
1. Review the Cisco advisory for affected versions. 2. Upgrade to a fixed version of Cisco IOS XR Software. 3. Apply the patch following Cisco's upgrade procedures without requiring a restart.
🔧 Temporary Workarounds
Disable Management Interface ACLs
allRemove or disable ACLs on the management interface for SSH, NetConf, and gRPC to prevent the bypass, but this reduces security controls.
configure terminal
no ipv4 access-list management_acl_name
commit
Use Network Segmentation
allImplement network-level controls (e.g., firewalls) to restrict access to the management interface instead of relying on device ACLs.
🧯 If You Can't Patch
- Apply strict network segmentation to isolate the management interface from untrusted networks.
- Monitor logs for unauthorized access attempts and implement intrusion detection systems.
🔍 How to Verify
Check if Vulnerable:
Check if the device is running an affected version of Cisco IOS XR Software on a Packet I/O infrastructure platform with ACLs configured for management services.Check Version:
show versionVerify Fix Applied:
After patching, verify the device is running a fixed version and test ACL functionality by attempting to bypass with controlled traffic.📡 Detection & Monitoring
Log Indicators:
- Unexpected SSH, NetConf, or gRPC connection attempts from blocked IP addresses in system logs.
Network Indicators:
- Traffic to management interface ports (e.g., SSH port 22) from sources that should be blocked by ACLs.
SIEM Query:
source_ip IN (blocked_ips) AND dest_port IN (22, 830, 57400) AND protocol IN (ssh, netconf, grpc)