CVE-2017-6743
Published: 17 July 2017
Summary
CVE-2017-6743 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 AC-6 (Least Privilege) 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. These flaws affect all versions of SNMP (1, 2c, and 3) and can be triggered by a crafted SNMP packet sent over IPv4 or IPv6. All devices running the affected software with SNMP enabled, and that have not explicitly excluded the relevant MIBs or OIDs, are 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 exploit the issue by sending a malicious packet directly to an affected device. Successful exploitation grants the attacker the ability to execute arbitrary code with full control of the system or to force a reload, resulting in denial of service.
Cisco security advisories recommend applying available workarounds and installing fixed software identified through the Cisco IOS Software Checker. Devices should be evaluated for exposure if SNMP is active without explicit exclusions for the affected objects.
The vulnerability appears in the CISA Known Exploited Vulnerabilities catalog, indicating confirmed real-world exploitation activity.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2017-15797
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 an attacker can send a crafted packet.
Enforces least-privilege restrictions on SNMP community strings, user credentials, and permitted MIB/OID access so an authenticated attacker cannot reach the vulnerable code paths.
Boundary-protection rules (e.g., ACLs, interface ACLs) can block SNMP traffic from unauthorized IPv4/IPv6 sources, preventing the crafted packet from ever arriving at the affected device.