CVE-2017-6738
Published: 17 July 2017
Summary
CVE-2017-6738 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 4.3% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog.
The strongest mitigations our analysis identified are NIST 800-53 CM-7 (Least Functionality) and SC-7 (Boundary Protection).
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 versions of SNMP (1, 2c, and 3) and can be triggered by a single crafted packet sent over IPv4 or IPv6; devices are considered vulnerable if SNMP is enabled and the affected MIBs or OIDs have not been explicitly excluded.
An authenticated remote attacker who knows the read-only community string (for SNMPv1/v2c) or possesses valid user credentials (for SNMPv3) can exploit the issue to execute arbitrary code with full system control or force a reload. Only traffic directed at the device itself can be used; unauthenticated or transit traffic is not sufficient.
Cisco Security Advisories recommend applying the documented workarounds and installing fixed releases identified by the Cisco IOS Software Checker. All SNMP-enabled devices should be treated as exposed until patched or mitigated.
The vulnerability appears in the CISA Known Exploited Vulnerabilities catalog, confirming observed in-the-wild exploitation.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2017-15792
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 requires applying vendor patches or workarounds that eliminate the SNMP buffer-overflow flaws before exploitation can succeed.
Enforces disabling SNMP or explicitly excluding the vulnerable MIBs/OIDs, removing the attack surface described in the CVE.
Boundary-protection mechanisms (e.g., ACLs) can restrict SNMP traffic to only authorized IPv4/IPv6 sources, blocking the crafted packets that trigger the overflow.