Advisories
Cisco IOS XE SNMP DoS Vulnerability (CVE‑2026‑20124) Forces Device Reloads
A flaw in Cisco IOS XE’s SNMP subsystem lets an authenticated attacker send a malformed request that crashes the device, causing it to reload and creating a denial‑of‑service. The issue affects all SNMP versions and requires valid community strings or SNMPv3 credentials. Cisco has released patches; no workarounds exist.
Overview
Cisco IOS XE software contains a critical vulnerability in the SNMP handling code. When an attacker sends a crafted SNMP packet, the device’s parser fails, forcing a reload and resulting in a temporary outage.
Technical Details
- Vulnerability type: improper error handling in SNMP request parsing.
- All SNMP versions (v1, v2c, v3) are affected.
- Requires authentication: SNMPv1/v2c read‑only or read‑write community string, or valid SNMPv3 user credentials.
- Exploit path: send a malformed SNMP message → crash → device reloads.
Impact
- Denial of Service: device becomes unavailable until it reloads.
- Potential disruption to network management and monitoring.
- High severity due to remote exploitation with legitimate credentials.
Mitigation
- Apply the official Cisco IOS XE software updates that patch the SNMP subsystem.
- No operational workarounds are available; disabling SNMP entirely is the only temporary measure.
- Verify that community strings and SNMPv3 users are tightly controlled to reduce risk.
RootPwn advises all organizations running Cisco IOS XE to check their firmware version and install the latest patch immediately.
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