CVE-2017-6736
Published: 17 July 2017
Summary
CVE-2017-6736 is a high-severity Improper Restriction of Operations within the Bounds of a Memory Buffer (CWE-119) vulnerability in Cisco Ios. Its CVSS base score is 8.8 (High).
Operationally, ranked in the top 0.5% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified are NIST 800-53 CM-7 (Least Functionality) and SI-2 (Flaw Remediation).
Deeper analysis
The vulnerability is a set of buffer overflow conditions in the Simple Network Management Protocol (SNMP) subsystem of Cisco IOS and IOS XE Software. The flaws affect all SNMP versions (1, 2c, and 3) and can be triggered by traffic directed to the device over IPv4 or IPv6; any system with SNMP enabled and without explicit exclusion of the affected MIBs or OIDs is considered vulnerable.
An authenticated remote attacker who knows the SNMP read-only community string (for versions 2c and earlier) or possesses valid user credentials (for version 3) can send a crafted SNMP packet to execute arbitrary code with full control of the device or force a reload. Exploitation requires no user interaction and can be performed from any network position that can reach the SNMP service.
Cisco Security Advisories recommend applying the documented workarounds or installing fixed software identified via the Cisco IOS Software Checker; all devices running affected releases should be considered at risk until mitigated. Public references include exploit code and additional tracking entries that confirm the issues were disclosed in June 2017.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2017-15790
Vulnerability details
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…
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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.
- CWE(s)
- KEV Date Added
- 03 March 2022
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly mitigates by disabling SNMP or explicitly excluding the vulnerable MIBs/OIDs so crafted packets cannot reach the buffer-overflow code paths.
Requires installation of the fixed Cisco IOS/IOS-XE releases identified by the IOS Software Checker, eliminating the SNMP buffer-overflow flaws.
Restricts IPv4/IPv6 traffic destined to UDP/161 (and any non-standard SNMP ports) to only authorized management hosts, blocking unauthenticated remote attackers.