CVE-2013-0340

expat 2.1.0 and earlier does not properly handle entities expansion unless an application developer uses the XML_SetEntityDeclHandler function, which allows remote attackers to cause a denial of service (resource consumption), send HTTP requests to intranet servers, or read arbitrary files via a crafted XML document, aka an XML External Entity (XXE) issue. NOTE: it could be argued that because expat already provides the ability to disable external entity expansion, the responsibility for resolving this issue lies with application developers; according to this argument, this entry should be REJECTed, and each affected application would need its own CVE.

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

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

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/221.html

References

• http://openwall.com/lists/oss-security/2013/02/22/3
• http://seclists.org/fulldisclosure/2021/Oct/61
• http://seclists.org/fulldisclosure/2021/Oct/62
• http://seclists.org/fulldisclosure/2021/Oct/63
• http://seclists.org/fulldisclosure/2021/Sep/33
• http://seclists.org/fulldisclosure/2021/Sep/34
• http://seclists.org/fulldisclosure/2021/Sep/35
• http://seclists.org/fulldisclosure/2021/Sep/38
• http://seclists.org/fulldisclosure/2021/Sep/39
• http://seclists.org/fulldisclosure/2021/Sep/40
• http://securitytracker.com/id?1028213
• http://www.openwall.com/lists/oss-security/2013/04/12/6
• http://www.openwall.com/lists/oss-security/2021/10/07/4
• http://www.osvdb.org/90634
• http://www.securityfocus.com/bid/58233
• https://lists.apache.org/thread.html/r41eca5f4f09e74436cbb05dec450fc2bef37b5d3e966aa7cc5fada6d%40%3Cannounce.apache.org%3E
• https://lists.apache.org/thread.html/rfb2c193360436e230b85547e85a41bea0916916f96c501f5b6fc4702%40%3Cusers.openoffice.apache.org%3E
• https://security.gentoo.org/glsa/201701-21
• https://support.apple.com/kb/HT212804
• https://support.apple.com/kb/HT212805
• https://support.apple.com/kb/HT212807
• https://support.apple.com/kb/HT212814
• https://support.apple.com/kb/HT212815
• https://support.apple.com/kb/HT212819