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Improper Handling of Exceptional Conditions in org.xwiki.platform:xwiki-platform-rendering-parser

Moderate
manuelleduc published GHSA-52vf-hvv3-98h7 Mar 1, 2023

Package

maven org.xwiki.platform:xwiki-platform-rendering-parser (Maven)

Affected versions

>= 6.0

Patched versions

13.10.10, 14.4.6, 14.9-rc-1

Description

Impact

Users with write rights can insert well-formed content that is not handled well by the parser. For instance, with xwiki/2.1, inserting a deeply nested group blocks (((( ((( ((( ((( .... ))) ))) ))) ))) (see the generator below to produce a large payload) can lead to the parser throwing a StackOverflowError.
As a consequence, some pages becomes unusable, including:

  • the user index (if the page containing the faulty content is a user page)
  • the page index

Note that on the page, the normal UI is completely missing and it is not possible to open the editor directly to revert the change as the stack overflow is already triggered while getting the title of the document. This means that it is quite difficult to remove this content once inserted.

Patches

This has been patched on XWiki 13.10.10, 14.4.6, and 14.9-rc-1.

Workarounds

A temporary solution to avoid Stack Overflow errors is to increase the memory allocated to the stack by using the -Xss JVM parameter (e.g., -Xss32m). This should allow the parser to pass and to fix the faulty content.
Note that we did not evaluated the consequence on other aspects of the system (e.g., performances), and should be only be used as a temporary solution.
Also, this does not prevent the issue to occur again with another content.
Consequently, it is strongly advised to upgrade to a version where the issue has been patched.

References

For more information

If you have any questions or comments about this advisory:

Payload Generator

The Javascript code below produces 32768 nested group blocks, around the Hello text.

let result = "(((\nHello\n)))";
for (let i = 0; i < 15; ++i) {
  result = result.replace("Hello", result);
}
console.log(result);

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVE ID

CVE-2023-26479

Weaknesses