CVE-2019-1969 - Improper Input Validation vulnerability in Cisco Nx-Os

047910
CVSS 5.0 - MEDIUM
Attack vector
NETWORK
Attack complexity
LOW
Privileges required
NONE
Confidentiality impact
NONE
Integrity impact
PARTIAL
Availability impact
NONE
network
low complexity
cisco
CWE-20
nessus

Summary

A vulnerability in the implementation of the Simple Network Management Protocol (SNMP) Access Control List (ACL) feature of Cisco NX-OS Software could allow an unauthenticated, remote attacker to perform SNMP polling of an affected device, even if it is configured to deny SNMP traffic. The vulnerability is due to an incorrect length check when the configured ACL name is the maximum length, which is 32 ASCII characters. An attacker could exploit this vulnerability by performing SNMP polling of an affected device. A successful exploit could allow the attacker to perform SNMP polling that should have been denied. The attacker has no control of the configuration of the SNMP ACL name.

Vulnerable Configurations

Part Description Count
OS
Cisco
4
Hardware
Cisco
64

Common Weakness Enumeration (CWE)

Common Attack Pattern Enumeration and Classification (CAPEC)

  • Buffer Overflow via Environment Variables
    This attack pattern involves causing a buffer overflow through manipulation of environment variables. Once the attacker finds that they can modify an environment variable, they may try to overflow associated buffers. This attack leverages implicit trust often placed in environment variables.
  • Server Side Include (SSI) Injection
    An attacker can use Server Side Include (SSI) Injection to send code to a web application that then gets executed by the web server. Doing so enables the attacker to achieve similar results to Cross Site Scripting, viz., arbitrary code execution and information disclosure, albeit on a more limited scale, since the SSI directives are nowhere near as powerful as a full-fledged scripting language. Nonetheless, the attacker can conveniently gain access to sensitive files, such as password files, and execute shell commands.
  • Cross Zone Scripting
    An attacker is able to cause a victim to load content into their web-browser that bypasses security zone controls and gain access to increased privileges to execute scripting code or other web objects such as unsigned ActiveX controls or applets. This is a privilege elevation attack targeted at zone-based web-browser security. In a zone-based model, pages belong to one of a set of zones corresponding to the level of privilege assigned to that page. Pages in an untrusted zone would have a lesser level of access to the system and/or be restricted in the types of executable content it was allowed to invoke. In a cross-zone scripting attack, a page that should be assigned to a less privileged zone is granted the privileges of a more trusted zone. This can be accomplished by exploiting bugs in the browser, exploiting incorrect configuration in the zone controls, through a cross-site scripting attack that causes the attackers' content to be treated as coming from a more trusted page, or by leveraging some piece of system functionality that is accessible from both the trusted and less trusted zone. This attack differs from "Restful Privilege Escalation" in that the latter correlates to the inadequate securing of RESTful access methods (such as HTTP DELETE) on the server, while cross-zone scripting attacks the concept of security zones as implemented by a browser.
  • Cross Site Scripting through Log Files
    An attacker may leverage a system weakness where logs are susceptible to log injection to insert scripts into the system's logs. If these logs are later viewed by an administrator through a thin administrative interface and the log data is not properly HTML encoded before being written to the page, the attackers' scripts stored in the log will be executed in the administrative interface with potentially serious consequences. This attack pattern is really a combination of two other attack patterns: log injection and stored cross site scripting.
  • Command Line Execution through SQL Injection
    An attacker uses standard SQL injection methods to inject data into the command line for execution. This could be done directly through misuse of directives such as MSSQL_xp_cmdshell or indirectly through injection of data into the database that would be interpreted as shell commands. Sometime later, an unscrupulous backend application (or could be part of the functionality of the same application) fetches the injected data stored in the database and uses this data as command line arguments without performing proper validation. The malicious data escapes that data plane by spawning new commands to be executed on the host.

Nessus

NASL familyCISCO
NASL idCISCO-SA-20190828-NXOS-SNMP-BYPASS.NASL
descriptionAccording to its self-reported version, Cisco NX-OS Software is affected by a vulnerability that allows an unauthenticated, remote attacker to perform SNMP polling of an affected device, even when it is configured to deny SNMP traffic. The cause of this vulnerability is an incorrect length check when the configured ACL name is 32 ASCII characters (the maximum length). Though the attacker has no control over the configuration of the SNMP ACL name, an attacker can exploit this vulnerability by performing SNMP polling of an affected device. This allows the attacker to perform SNMP polling that should have been denied. With SNMP Version 2c or earlier, to exploit this vulnerability the attacker must know the SNMP read-only community string for the affected system. The community string is a password applied to a device which restricts both read-only and read-write access to the SNMP data on the device. Community strings should be treated like all passwords: they must be non-trivial and changed at regular intervals in accordance with network security policies. With SNMP Version 3, the attacker must have user credentials for the affected system. Please see the included Cisco BID and Cisco Security Advisory for more information
last seen2020-03-17
modified2019-09-13
plugin id128760
published2019-09-13
reporterThis script is Copyright (C) 2019 and is owned by Tenable, Inc. or an Affiliate thereof.
sourcehttps://www.tenable.com/plugins/nessus/128760
titleCisco NX-OS Software SNMP Access Control List Configuration Name Bypass Vulnerability (CVE-2019-1969)