Summary
xwiki vulnerable to Improper Handling of Exceptional Conditions
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:
- Open an issue in Jira
- Email us at Security ML
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);
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.
CVE-2023-26479 has a CVSS score of 6.5 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (13.10.10, 14.4.6, 14.9-rc-1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
This has been patched on XWiki 13.10.10, 14.4.6, and 14.9-rc-1.
Frequently Asked Questions
- What is CVE-2023-26479? CVE-2023-26479 is a medium-severity security vulnerability in org.xwiki.platform:xwiki-platform-rendering-parser (maven), affecting versions >= 6.0, < 13.10.10. It is fixed in 13.10.10, 14.4.6, 14.9-rc-1.
- How severe is CVE-2023-26479? CVE-2023-26479 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of org.xwiki.platform:xwiki-platform-rendering-parser are affected by CVE-2023-26479? org.xwiki.platform:xwiki-platform-rendering-parser (maven) versions >= 6.0, < 13.10.10 is affected.
- Is there a fix for CVE-2023-26479? Yes. CVE-2023-26479 is fixed in 13.10.10, 14.4.6, 14.9-rc-1. Upgrade to this version or later.
- Is CVE-2023-26479 exploitable, and should I be worried? Whether CVE-2023-26479 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2023-26479 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2023-26479?
- Upgrade
org.xwiki.platform:xwiki-platform-rendering-parserto 13.10.10 or later - Upgrade
org.xwiki.platform:xwiki-platform-rendering-parserto 14.4.6 or later - Upgrade
org.xwiki.platform:xwiki-platform-rendering-parserto 14.9-rc-1 or later
- Upgrade