CVE-2025-20154 Overview
A vulnerability exists in the Two-Way Active Measurement Protocol (TWAMP) server feature of Cisco IOS Software, Cisco IOS XE Software, and Cisco IOS XR Software that could allow an unauthenticated, remote attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition. This vulnerability is due to out-of-bounds array access when processing specially crafted TWAMP control packets.
Critical Impact
Successful exploitation allows remote attackers to crash affected Cisco network devices without authentication, causing network outages and service disruption across enterprise infrastructure.
Affected Products
- Cisco IOS Software (all vulnerable versions)
- Cisco IOS XE Software (all vulnerable versions)
- Cisco IOS XR Software versions 6.5.1 through 24.3.1 (ipsla_ippm_server process affected when debugs are enabled)
Discovery Timeline
- May 7, 2025 - CVE-2025-20154 published to NVD
- July 31, 2025 - Last updated in NVD database
Technical Details for CVE-2025-20154
Vulnerability Analysis
This vulnerability affects the TWAMP server implementation, which is a network performance measurement protocol defined in RFC 5357. The flaw exists in how the affected software processes incoming TWAMP control packets. When a malformed packet is received, the software fails to properly validate array boundaries before accessing memory locations, leading to an out-of-bounds array access condition. This memory safety violation causes the device to crash and reload.
For Cisco IOS and IOS XE Software, exploitation results in a complete device reload, causing immediate loss of network connectivity through the affected device. For Cisco IOS XR Software, the impact is more limited—only the ipsla_ippm_server process reloads unexpectedly, and this occurs only when debug logging is enabled for that process.
Root Cause
The root cause is improper input validation (CWE-20) in the TWAMP control packet parsing logic. The software does not adequately validate the bounds of data within incoming TWAMP control packets before using that data as an index into internal arrays. This allows an attacker to craft packets that cause the software to access memory outside the intended array boundaries, triggering a crash condition.
Attack Vector
An attacker can exploit this vulnerability by sending specially crafted TWAMP control packets to an affected device over the network. The attack requires:
- Network accessibility to the TWAMP server port on the target device
- The TWAMP server feature must be enabled on the device
- No authentication is required to send the malicious packets
The attacker crafts TWAMP control packets with malformed data fields designed to trigger the out-of-bounds array access condition. When the vulnerable device processes these packets, it causes an immediate device reload for Cisco IOS and IOS XE, or a process crash on Cisco IOS XR when debugging is active.
Due to the nature of the vulnerability (improper input validation in protocol parsing), exploitation does not require valid credentials or prior authenticated access to the device.
Detection Methods for CVE-2025-20154
Indicators of Compromise
- Unexpected device reloads or crashes with crash dumps referencing TWAMP-related processes
- Repeated ipsla_ippm_server process restarts on Cisco IOS XR systems
- Unusual TWAMP control packet traffic patterns from external or unexpected sources
- System logs indicating memory access violations or segmentation faults in TWAMP-related code paths
Detection Strategies
- Monitor network traffic for abnormal TWAMP control packets on port 862 (standard TWAMP control port)
- Implement intrusion detection rules to identify malformed TWAMP packets with suspicious payload characteristics
- Review device crash logs and crash dump files for evidence of out-of-bounds access in TWAMP processing functions
- Deploy network behavior analysis to detect unexpected TWAMP traffic from unauthorized sources
Monitoring Recommendations
- Enable syslog monitoring for device reload events and correlate with TWAMP traffic patterns
- Configure SNMP traps for unexpected device restarts and process failures
- Implement NetFlow or similar flow analysis to track TWAMP traffic volumes and sources
- Review AAA accounting logs for any configuration changes to TWAMP server settings
How to Mitigate CVE-2025-20154
Immediate Actions Required
- Disable the TWAMP server feature if it is not required for network operations
- Implement access control lists (ACLs) to restrict TWAMP traffic to trusted management stations only
- Apply network segmentation to limit exposure of management interfaces
- Upgrade affected devices to patched software versions as identified in Cisco's security advisory
Patch Information
Cisco has released security patches addressing this vulnerability. Administrators should consult the Cisco Security Advisory for specific fixed software versions and upgrade guidance. The advisory provides detailed information on which software releases contain the fix for each affected platform (IOS, IOS XE, and IOS XR).
Workarounds
- Disable the TWAMP server feature using configuration commands if the feature is not operationally required
- Configure infrastructure ACLs to permit TWAMP traffic only from authorized IP addresses
- For Cisco IOS XR, disable TWAMP-related debugging to reduce the attack surface (process only crashes when debugs are enabled)
- Implement control plane policing (CoPP) to rate-limit TWAMP control traffic to the device
# Example: Disable TWAMP server on Cisco IOS/IOS XE
configure terminal
no ip sla server twamp
end
write memory
# Example: Apply ACL to restrict TWAMP access
configure terminal
ip access-list extended TWAMP-RESTRICT
permit udp host 10.0.0.100 any eq 862
deny udp any any eq 862
exit
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
