XML External Entity (XXE) Injection Affecting typo3/cms package, versions >=10.4.0, <10.4.10


Severity

Recommended
0.0
low
0
10

CVSS assessment made by Snyk's Security Team. Learn more

Threat Intelligence

EPSS
0.07% (34th percentile)

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  • Snyk IDSNYK-PHP-TYPO3CMS-1044046
  • published24 Nov 2020
  • disclosed24 Nov 2020
  • creditUnknown

Introduced: 24 Nov 2020

CVE-2020-26229  (opens in a new tab)
CWE-611  (opens in a new tab)

How to fix?

Upgrade typo3/cms to version 10.4.10 or higher.

Overview

typo3/cms is a free open source Content Management Framework.

Affected versions of this package are vulnerable to XML External Entity (XXE) Injection. RSS widgets are susceptible to XML external entity processing.This vulnerability is reasonable, but is theoretical - it was not possible to actually reproduce the vulnerability with current PHP versions of supported and maintained system distributions.At least with libxml2 version 2.9, the processing of XML external entities is disabled per default - and cannot be exploited. Besides that, a valid backend user account is needed.

Details

XXE Injection is a type of attack against an application that parses XML input. XML is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. By default, many XML processors allow specification of an external entity, a URI that is dereferenced and evaluated during XML processing. When an XML document is being parsed, the parser can make a request and include the content at the specified URI inside of the XML document.

Attacks can include disclosing local files, which may contain sensitive data such as passwords or private user data, using file: schemes or relative paths in the system identifier.

For example, below is a sample XML document, containing an XML element- username.

<xml>
<?xml version="1.0" encoding="ISO-8859-1"?>
   <username>John</username>
</xml>

An external XML entity - xxe, is defined using a system identifier and present within a DOCTYPE header. These entities can access local or remote content. For example the below code contains an external XML entity that would fetch the content of /etc/passwd and display it to the user rendered by username.

<xml>
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE foo [
   <!ENTITY xxe SYSTEM "file:///etc/passwd" >]>
   <username>&xxe;</username>
</xml>

Other XXE Injection attacks can access local resources that may not stop returning data, possibly impacting application availability and leading to Denial of Service.

References

CVSS Scores

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