Cisco IOS XR Vulnerability Poses a Threat to Network Security

Cisco has issued a warning about a critical vulnerability in its IOS XR software that, if exploited, could lead to a Denial-of-Service (DoS) attack. This vulnerability, identified as CVE-2025-20115, has been assigned a CVSS score of 8.6, indicating a high severity level.

The flaw originates from memory corruption in the BGP confederation implementation. If a BGP update contains an AS_CONFED_SEQUENCE attribute with 255 or more Autonomous System (AS) numbers, a buffer overflow occurs, causing the BGP process to crash.

An attacker can exploit this vulnerability by sending specially crafted BGP update packets, which could force the BGP process to restart, leading to a network-wide service disruption.

Affected Cisco IOS XR Versions:

✅ 7.11 and earlier
✅ 24.1 and earlier
✅ 24.2 up to 24.2.20

If BGP confederation is enabled on these versions, the network is vulnerable.

🔐 Security Recommendations

1. Update Software (Best Solution)

Cisco has released fixed versions that address this vulnerability:

🔹 24.2.21 (upcoming version)
🔹 24.3.1
🔹 24.4

It is highly recommended to upgrade as soon as possible.

2. Alternative Mitigation: Limiting the Vulnerability

If an immediate update is not feasible, Cisco recommends restricting the AS_CONFED_SEQUENCE attribute to 254 or fewer AS numbers using a routing policy:

1️⃣ Create a route policy to block BGP updates with long AS paths:

2️⃣ Apply this policy to BGP neighbor configurations:

This configuration automatically blocks malicious BGP updates with long AS paths, reducing the risk of exploitation.

⚠ Additional Security Measures

🔹 Check Network Configuration
To verify if a device is vulnerable, run the following command:

If the output contains “bgp confederation peers”, the system may be at risk.

🔹 Enhance Security Monitoring
Keep an eye out for suspiciously long AS paths in BGP updates and take immediate action if necessary.

🔹 Inform Network Administrators
All network security professionals should be made aware of this vulnerability and implement necessary countermeasures.

🔴 Conclusion

CVE-2025-20115 is a critical vulnerability in Cisco IOS XR that can cause complete network failure. Attackers can exploit it to force the BGP process to restart, leading to severe disruptions.

To protect your network, it is crucial to update the software as soon as possible or implement the recommended AS_CONFED_SEQUENCE filtering policy.

🚨 Key takeaway: Always keep your systems updated and enhance security monitoring! 🚨