CVE-2025-20352: SNMP Stack Buffer Overflow in Cisco IOS and IOS XE (DoS & RCE)
HERMES
HERMES THREAT SCORE & NETWORK CORE RESILIENCE
Target:Cisco IOS and IOS XE Software SNMP Subsystem Confidence: 98%
85 / 100
Dimension Breakdown
Exploitability 18 / 20
Threat Activity 18 / 20
Weaponization 18 / 20
Exposure 17 / 20
Prevalence 20 / 20
Impact 17 / 20
Exploit Maturity 19 / 20
Attack Chain Potential 17 / 20
Divergence & Operational Rationale
Hermes assesses CVE-2025-20352 at an HTS of 85 (HIGH). Cataloged in CISA KEV, this flaw allows any internal user with read-only SNMP access (frequently accessible across campus LANs) to trigger repeated reloads of core switches and routers, causing widespread enterprise connectivity blackouts.
🕸️ Connected Knowledge Graph & Provenance
CVE-2025-20352: SNMP Stack Buffer Overflow in Cisco IOS and IOS XE (DoS & RCE)VULNERABILITY
Connected Nodes: 0
1. Identification
Section titled “1. Identification”| Parameter | Technical Specification | Operational Impact |
|---|---|---|
| CVE Identifier | CVE-2025-20352 | Cisco Advisory cisco-sa-snmp-x4LPhte |
| Associated CWE | CWE-121: Stack-based Buffer Overflow | Memory corruption in SNMP packet parser |
| CVSS v3.1 Score | 7.7 HIGH (DoS) / Root RCE if admin | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H |
| Applicable CPEs | cpe:2.3:o:cisco:ios:*:*:*:*:*:*:*:*cpe:2.3:o:cisco:ios_xe:*:*:*:*:*:*:*:* | Catalyst, ISR, ASR enterprise hardware |
| Fixed Versions | Official fixed releases specified in Cisco September 2025 advisory | Software image upgrade required |
2. Exploitation
Section titled “2. Exploitation”- CISA KEV: Added on September 29, 2025.
- EPSS Score: 0.39447 (Percentile: 98.5%).
- Operational Status: Confirmed in-the-wild exploitation. Exploited via crafted UDP port 161 packets.
- Prerequisites: Requires read-only SNMPv1/v2c community strings or valid SNMPv3 credentials to trigger unhandled stack corruption and immediate system reload.
3. Detection and Forensics
Section titled “3. Detection and Forensics”Suricata / Snort Rule
Section titled “Suricata / Snort Rule”alert udp any any -> $HOME_NET 161 (msg:"HERMES - Malformed SNMP Packet Potential CVE-2025-20352"; content:"|30|"; depth:1; dsize:>1400; classtype:attempted-dos; sid:202520352; rev:1;)MITRE ATT&CK
Section titled “MITRE ATT&CK”- T1498: Network Denial of Service
- T1499: Endpoint Denial of Service
4. Remediation and Hardening
Section titled “4. Remediation and Hardening”- Apply Software Upgrades: Upgrade Cisco IOS and IOS XE firmware to patched releases.
- Enforce SNMPv3: Retire legacy SNMPv1/v2c cleartext strings and enforce authenticated and encrypted SNMPv3 (AuthPriv).
- Infrastructure ACLs: Apply strict ingress access control lists to UDP port 161, permitting access only from dedicated network management stations (NMS).
5. Enterprise Exploitation Scenario
Section titled “5. Enterprise Exploitation Scenario”« What happens if this vulnerability is exploited in an enterprise? »
Section titled “« What happens if this vulnerability is exploited in an enterprise? »”
- Internal Reconnaissance: A rogue insider or compromised workstation identifies read-only SNMP strings (
public) exposed across the corporate intranet.- Denial-of-Service Flood: The attacker transmits crafted SNMP payloads targeting the management IPs of core routing and switching gear.
- Infrastructure Cascade Reload: The devices trigger memory exceptions and crash simultaneously, disrupting routing tables and dynamic trunking.
- Complete Business Disruption: Enterprise networks suffer immediate outage, halting internal ERP connectivity, voice-over-IP communications, and internet breakout.