ZeroHour

CVE-2017-6740

KEVmass

SNMP Buffer Overflow Allows Authenticated RCE in Cisco IOS and IOS XE

CISA: Cisco IOS and IOS XE Software SNMP Remote Code Execution Vulnerability

CVSS 3.1
8.8 high
EPSS
11%p96
Published
()
KEV added
AI analysis

The SNMP subsystem of Cisco IOS and IOS XE Software contains a buffer overflow (CWE-119) that allows an authenticated, remote attacker to execute arbitrary code or force the device to reload by sending a crafted SNMP packet over IPv4 or IPv6 to an affected system. Because only traffic directed to the device can trigger the flaw, exploitation requires the SNMP read-only community string (for SNMPv1/v2c) or valid SNMPv3 user credentials. A successful attack can yield full control of the router or switch, making internet-facing and core infrastructure devices the primary risk. All devices running IOS or IOS XE with SNMP enabled — SNMP versions 1, 2c, and 3 — should be considered vulnerable unless the affected MIBs/OIDs have been explicitly excluded. The flaw is listed in CISA's Known Exploited Vulnerabilities catalog (added 2022-03-03), and EPSS estimates an 10.9% probability of exploitation within 30 days (96th percentile), although no public PoC is known.

What to do: Identify affected devices with the Cisco IOS Software Checker and upgrade IOS/IOS XE to a fixed release per Cisco's advisory. If patching is delayed, restrict SNMP access with ACLs to trusted management hosts, disable SNMP if unused, or apply Cisco's workaround of excluding the affected MIBs/OIDs. Verify which devices have SNMP enabled and audit community strings and SNMPv3 credentials, since exploitation requires them.

Affected
cisco iosall versions of IOS with SNMP enabled (SNMPv1, v2c, v3); specific fixed releases via Cisco IOS Software Checker
cisco ios xeall versions of IOS XE with SNMP enabled (SNMPv1, v2c, v3); specific fixed releases via Cisco IOS Software Checker
Estimated exposure
masshundreds of thousands of internet-exposed Cisco IOS/IOS XE devices, with millions installed across enterprise, ISP, and data-center networks — Cisco IOS/IOS XE is one of the most widely deployed network operating systems globally, and public internet-wide scans consistently show SNMP on hundreds of thousands of Cisco routers and switches, so well over 100k exposed systems is a…

Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.

Description

The Simple Network Management Protocol (SNMP) subsystem of Cisco IOS and IOS XE Software contains multiple vulnerabilities that could allow an authenticated, remote attacker to remotely execute code on an affected system or cause an affected system to reload. An attacker could exploit these vulnerabilities by sending a crafted SNMP packet to an affected system via IPv4 or IPv6. Only traffic directed to an affected system can be used to exploit these vulnerabilities. The vulnerabilities are due to a buffer overflow condition in the SNMP subsystem of the affected software. The vulnerabilities affect all versions of SNMP - Versions 1, 2c, and 3. To exploit these vulnerabilities via SNMP Version 2c or earlier, the attacker must know the SNMP read-only community string for the affected system. To exploit these vulnerabilities via SNMP Version 3, the attacker must have user credentials for the affected system. A successful exploit could allow the attacker to execute arbitrary code and obtain full control of the affected system or cause the affected system to reload. Customers are advised to apply the workaround as contained in the Workarounds section below. Fixed software information is available via the Cisco IOS Software Checker. All devices that have enabled SNMP and have not explicitly excluded the affected MIBs or OIDs should be considered vulnerable. There are workarounds that address these vulnerabilities.

CISA Known Exploited Vulnerability
Affected
Cisco IOS and IOS XE Software
Required action
Apply updates per vendor instructions.
Due date
Ransomware use
Unknown
Vendors
cisco
Products
ios, ios xe
Weakness
CWE-119
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

In the news

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