SNMP Remote Code Execution Vulnerabilities in Cisco IOS and IOS XE Software

CVE numbers – CVE-2017-6736, CVE-2017-6737, CVE-2017-6738, CVE-2017-6739 , CVE-2017-6740, CVE-2017-6741, CVE-2017-6742, CVE-2017-6743 and CVE-2017-6744.

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. 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.

Cisco has released software updates that address these vulnerabilities. There are workarounds that address these vulnerabilities.

These vulnerabilities affect Cisco devices that are running a vulnerable release of Cisco IOS Software or Cisco IOS XE Software. These vulnerabilities affect all versions of SNMP, versions 1, 2c, and 3.

For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.

Devices configured with any of the following MIBs are vulnerable:

• ADSL-LINE-MIB
• ALPS-MIB
• CISCO-ADSL-DMT-LINE-MIB
• CISCO-AUTH-FRAMEWORK-MIB
• CISCO-BSTUN-MIB
• CISCO-MAC-AUTH-BYPASS-MIB
• CISCO-SLB-EXT-MIB
• CISCO-VOICE-DNIS-MIB
• CISCO-VOICE-NUMBER-EXPANSION-MIB
• TN3270E-RT-MIB

All of the MIBs listed above are enabled by default when SNMP is enabled. Some of the MIBs may not be present on all systems or versions but are enabled when present.

Administrators may be accustomed to utilizing the show snmp mib command in privileged EXEC mode to display a list of enabled MIBs on a device. Not all of the MIBs will be displayed in the output of the show snmp mib command but may still be enabled. Customers are advised to implement the entire exclude list as detailed in the Workarounds section of the advisory.

Further details at – https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170629-snmp