CVE-2023-45139 (published 2024-01-10T16:15Z)

fontTools is a library for manipulating fonts, written in Python. The subsetting module has a XML External Entity Injection (XXE) vulnerability which allows an attacker to resolve arbitrary entities when a candidate font (OT-SVG fonts), which contains a SVG table, is parsed. This allows attackers to include arbitrary files from the filesystem fontTools is running on or make web requests from the host system. This vulnerability has been patched in version 4.43.0.

CVSS v3 base score: 7.5, HIGH (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N)

Weakness information:
cwe_id: CWE-611
cwe_name: Improper Restriction of XML External Entity Reference
description: 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.
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.
         
         

Fix information:
repo_url: https://github.com/fonttools/fonttools
commit_details: repo_url: https://github.com/fonttools/fonttools
author: Cosimo Lupo
author_date: 2023-09-15 16:50:38+02:00
msg: subset: parse OT-SVG with resolve_entities=False

to guard against XXE attacks as recommended in https://codeql.github.com/codeql-query-help/python/py-xxe/
repository: repo_url: https://github.com/fonttools/fonttools
repo_name: fonttools/fonttools
description: A library to manipulate font files from Python.
repo_language: Python
owner: fonttools
file_changes: filename: svg.py
change_type: ModificationType.MODIFY
diff: @@ -225,6 +225,9 @@ def subset_glyphs(self, s) -> bool:
                 # ignore blank text as it's not meaningful in OT-SVG; it also prevents
                 # dangling tail text after removing an element when pretty_print=True
                 remove_blank_text=True,
+                # don't replace entities; we don't expect any in OT-SVG and they may
+                # aboused for XXE attacks
+                resolve_entities=False,
             ),
         )
 

programming_language: Python