Attacker Value
High
(1 user assessed)
Exploitability
Moderate
(1 user assessed)
User Interaction
None
Privileges Required
None
Attack Vector
Network
2

CVE-2023-38490

Disclosure Date: July 27, 2023 •
CVE-2023-38490 CVSS v3 Base Score: 10.0
Add MITRE ATT&CK tactics and techniques that apply to this CVE.

Description

Kirby is a content management system. A vulnerability in versions prior to 3.5.8.3, 3.6.6.3, 3.7.5.2, 3.8.4.1, and 3.9.6 only affects Kirby sites that use the Xml data handler (e.g. Data::decode($string, 'xml')) or the Xml::parse() method in site or plugin code. The Kirby core does not use any of the affected methods.

XML External Entities (XXE) is a little used feature in the XML markup language that allows to include data from external files in an XML structure. If the name of the external file can be controlled by an attacker, this becomes a vulnerability that can be abused for various system impacts like the disclosure of internal or confidential data that is stored on the server (arbitrary file disclosure) or to perform network requests on behalf of the server (server-side request forgery, SSRF).

Kirby’s Xml::parse() method used PHP’s LIBXML_NOENT constant, which enabled the processing of XML external entities during the parsing operation. The Xml::parse() method is used in the Xml data handler (e.g. Data::decode($string, 'xml')). Both the vulnerable method and the data handler are not used in the Kirby core. However they may be used in site or plugin code, e.g. to parse RSS feeds or other XML files. If those files are of an external origin (e.g. uploaded by a user or retrieved from an external URL), attackers may be able to include an external entity in the XML file that will then be processed in the parsing process. Kirby sites that don’t use XML parsing in site or plugin code are not affected.

The problem has been patched in Kirby 3.5.8.3, 3.6.6.3, 3.7.5.2, 3.8.4.1, and 3.9.6. In all of the mentioned releases, the maintainers have removed the LIBXML_NOENT constant as processing of external entities is out of scope of the parsing logic. This protects all uses of the method against the described vulnerability.

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1
Ratings
  • Attacker Value
    High
  • Exploitability
    Medium
Easy to weaponizeUnauthenticatedVulnerable in uncommon configuration
Technical Analysis

The XXE is in a function (Xml::parse) that is part of the core library but is not used directly in the CMS. So to be vulnerable, one has to have made a custom page or installed an extension using this vulnerable function.
Else it’s pretty handy and is present in nearly all versions of the CMS until the patch.

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CVSS V3 Severity and Metrics
Base Score:
10.0 Critical
Impact Score:
5.8
Exploitability Score:
3.9
Vector:
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N
Attack Vector (AV):
Network
Attack Complexity (AC):
Low
Privileges Required (PR):
None
User Interaction (UI):
None
Scope (S):
Changed
Confidentiality (C):
High
Integrity (I):
High
Availability (A):
None

General Information

Offensive Application
Unknown
Utility Class
Unknown
Ports
Unknown
OS
Unknown
Vulnerable Versions
kirby < 3.5.8.3
kirby >= 3.6.0, < 3.6.6.3
kirby >= 3.7.0, < 3.7.5.2
kirby >= 3.8.0, < 3.8.41
kirby >= 3.9.0, < 3.9.6
Prerequisites
Unknown
Discovered By
Unknown
PoC Author
Unknown
Metasploit Module
Unknown
Reporter
Unknown

Vendors

  • getkirby

Products

  • kirby
Technical Analysis