CVE Vulnerabilities

CVE-2022-20812

Improper Neutralization of Null Byte or NUL Character

Published: Jul 06, 2022 | Modified: Nov 21, 2024
CVSS 3.x
6.5
MEDIUM
Source:
NVD
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H
CVSS 2.x
8.5 HIGH
AV:N/AC:L/Au:S/C:N/I:C/A:C
RedHat/V2
RedHat/V3
Ubuntu

Multiple vulnerabilities in the API and in the web-based management interface of Cisco Expressway Series and Cisco TelePresence Video Communication Server (VCS) could allow a remote attacker to overwrite arbitrary files or conduct null byte poisoning attacks on an affected device. Note: Cisco Expressway Series refers to the Expressway Control (Expressway-C) device and the Expressway Edge (Expressway-E) device. For more information about these vulnerabilities, see the Details section of this advisory.

Weakness

The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes NUL characters or null bytes when they are sent to a downstream component.

Affected Software

Name Vendor Start Version End Version
Expressway Cisco * x14.0.7 (excluding)
Telepresence_video_communication_server Cisco * x14.0.7 (excluding)

Potential Mitigations

  • Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
  • When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
  • Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

References