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CVE-2017-6743Cisco IOS and IOS XE Software SNMP Remote Code Execution Vulnerability

Patch nowHigh8.8Exploited, CISA due date 2022-03-24EPSS 11%, higher than 96% of scored CVEs

CVE-2017-6743 is a memory buffer error in Cisco IOS and IOS XE Software, rated high (8.8 on CVSS 3.1).

Why this priority: Exploited in the wild: listed in CISA's KEV catalog.

Published · Updated · NVD status: Analyzed

What it is

Code reads or writes outside the memory it was given, which can corrupt the process.

How it is reached

An attacker can exploit it over the network, with an ordinary user account, and nobody has to click anything.

What an attacker gains

A successful attack can read the data it protects, change data or behaviour and take it offline. In practice, this kind of flaw lets an attacker crash the process, read memory, or in the worst case run code.

Is it being exploited?

CISA added it to the Known Exploited Vulnerabilities catalog on 2022-03-03: it is being exploited in the wild. EPSS estimates a 11% chance of exploitation activity in the next 30 days, higher than 96% of scored CVEs.

What to do

  1. Treat it as urgent: it is on CISA's KEV list. CISA's deadline for US federal agencies: 2022-03-24.
  2. No fixed version is listed yet. Find every place Cisco IOS and IOS XE Software runs, watch the references for a fix, and plan a replacement if it is no longer supported.
  3. While there is no fix, review who holds accounts that can reach it.
  4. Check exposed instances for signs of compromise, not only for the version.

Description from NVD

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.

What this means for your architecture.

A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.

Components it touches

  • Network edge devices: VPNs, firewalls, routers and gateways. They sit between the internet and internal networks, so a flaw in one is often the first step into everything behind it.
  • Operating systems on servers, workstations or devices. Everything on the host inherits the flaw.
  • Native code: operating systems, browsers and firmware. The flaw sits wherever native code reads untrusted data.
  • Network appliances and media or file parsers. The flaw sits wherever native code reads untrusted data.

Trust boundaries in play

  • Authenticated network access. An account is needed, so exposure follows who can sign in: customers, partners or staff.
  • Wherever native code reads untrusted data. An attacker who crosses it can crash the process, read memory, or in the worst case run code.

Questions to answer about your own systems

  • Where does Cisco IOS and IOS XE Software run in your systems, and at which version?
  • Which of those instances can be reached from the internet or partner networks?
  • What can it reach once compromised: which data stores, secrets and services?
See how Veriom maps an architectureTake the interactive tour

Read more

Sources

  • CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
  • Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
  • Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
  • Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.