CVE Vulnerabilities

CVE-2021-1369

Improper Restriction of XML External Entity Reference

Published: Apr 29, 2021 | Modified: May 05, 2021
CVSS 3.x
5.4
MEDIUM
Source:
NVD
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L
CVSS 2.x
5.5 MEDIUM
AV:N/AC:L/Au:S/C:P/I:N/A:P
RedHat/V2
RedHat/V3
Ubuntu

A vulnerability in the REST API of Cisco Firepower Device Manager (FDM) On-Box Software could allow an authenticated, remote attacker to gain read and write access to information that is stored on an affected device. This vulnerability is due to the improper handling of XML External Entity (XXE) entries when parsing certain XML files. An attacker could exploit this vulnerability by sending malicious requests that contain references in XML entities to an affected system. A successful exploit could allow the attacker to retrieve files from the local system, resulting in the disclosure of sensitive information or causing a partial denial of service (DoS) condition on the affected device.

Weakness

The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.

Affected Software

Name Vendor Start Version End Version
Firepower_device_manager Cisco 6.6.0 *
Firepower_device_manager Cisco * *

Extended Description

XML documents optionally contain a Document Type Definition (DTD), which, among other features, enables the definition of XML entities. It is possible to define an entity by providing a substitution string in the form of a URI. The XML parser can access the contents of this URI and embed these contents back into the XML document for further processing. By submitting an XML file that defines an external entity with a file:// URI, an attacker can cause the processing application to read the contents of a local file. For example, a URI such as “file:///c:/winnt/win.ini” designates (in Windows) the file C:\Winnt\win.ini, or file:///etc/passwd designates the password file in Unix-based systems. Using URIs with other schemes such as http://, the attacker can force the application to make outgoing requests to servers that the attacker cannot reach directly, which can be used to bypass firewall restrictions or hide the source of attacks such as port scanning. Once the content of the URI is read, it is fed back into the application that is processing the XML. This application may echo back the data (e.g. in an error message), thereby exposing the file contents.

Potential Mitigations

References