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How the CVE Works
CVE-2025-20189 exploits improper memory management in Cisco IOS XE’s Cisco Express Forwarding (CEF) when processing ARP messages. An adjacent attacker sends crafted ARP packets at a high rate, overwhelming the router’s memory allocation. This leads to resource exhaustion, forcing a reload of the active Route Switch Processor (RSP3C). Without redundancy, the entire router reboots, causing prolonged downtime. The flaw stems from insufficient validation of ARP message handling, allowing malicious inputs to trigger memory leaks.
DailyCVE Form
Platform: Cisco IOS XE
Version: ASR 903 (RSP3C)
Vulnerability: Memory exhaustion via ARP flood
Severity: Critical
Date: 08/05/2025
Prediction: Patch expected by 10/2025
What Undercode Say
show arp | include suspicious debug cef memory allocation monitor process cpu | exclude 0.00%
How Exploit
1. Crafted ARP packets sent at 10k+/sec
2. Target RSP3C via adjacent network segment
3. Sustained flood triggers RSP crash
Protection from this CVE
- Apply Cisco patch (when released)
- Enable RSP redundancy
- Rate-limit ARP traffic
Impact
- Full router reload (5+ mins downtime)
- Service disruption for all routed traffic
- No remote code execution
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Sources:
Reported By: nvd.nist.gov
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Undercode
