Summary
docx4j: Stack Overflow via Cyclic w:basedOn Style Chain leads to Denial of Service
docx4j's PropertyResolver and several adjacent helpers recursively walk the OpenXML style inheritance chain (w:basedOn) without cycle detection.
A WordprocessingML document containing a cyclic style chain (for example, Style A based on B and Style B based on A) causes unbounded recursion and a java.lang.StackOverflowError within the property-resolution code path.
These helpers are used by operations that require effective style resolution, including common conversion and TOC-related paths. As a result, most server-side pipelines that accept a user-supplied docx and process it through docx4j can likely be crashed by a file containing a cyclic style reference.
Details
Representative snippet: PropertyResolver.fillPPrStack
private void fillPPrStack(String styleId, Stack<PPr> pPrStack) {
Style style = liveStyles.get(styleId);
...
// if it is based on, recurse
if (style.getBasedOn() == null) {
log.debug("Style " + styleId + " is a root style.");
} else if (style.getBasedOn().getVal() != null) {
String basedOnStyleName = style.getBasedOn().getVal();
fillPPrStack(basedOnStyleName, pPrStack); // ← unbounded recursion
...
Credits
Thanks to Koh You Liang (@Isopach) for responsibly disclosing this issue.
Impact
This is a denial of service against a server-side application that processes untrusted docx files via docx4j.
An upload causes the processing thread to be terminated with StackOverflowError which may crash the worker thread, degrade the thread pool, or evade normal per-request CPU and heap-memory safeguards in containers and serverless functions (because the failure mode is thread-stack exhaustion rather than gradual resource consumption).
The attack depends on the host application's access controls and requires no user interaction beyond submitting the file. Detection is difficult because the file is a well-formed OOXML package containing ordinary style elements, and passes standard antivirus and content-inspection rules.
Severity: High for server-side applications that process untrusted DOCX files using docx4j style/property resolution (unless the application catches StackOverflowError, isolates conversion in disposable worker processes, restarts workers cleanly, and the practical impact is only failure of one request). Severity may be Medium where document upload requires authentication, processing is isolated, or the failure is limited to a single request/worker.
The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.
CVE-2026-53752 has a CVSS score of 7.5 (High). The vector is network-reachable, no 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 (11.5.14); 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.
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Frequently Asked Questions
- What is CVE-2026-53752? CVE-2026-53752 is a high-severity allocation of resources without limits or throttling vulnerability in org.docx4j:docx4j-core (maven), affecting versions <= 11.5.13. It is fixed in 11.5.14. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
- How severe is CVE-2026-53752? CVE-2026-53752 has a CVSS score of 7.5 (High). 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.docx4j:docx4j-core are affected by CVE-2026-53752? org.docx4j:docx4j-core (maven) versions <= 11.5.13 is affected.
- Is there a fix for CVE-2026-53752? Yes. CVE-2026-53752 is fixed in 11.5.14. Upgrade to this version or later.
- Is CVE-2026-53752 exploitable, and should I be worried? Whether CVE-2026-53752 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-2026-53752 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-2026-53752? Upgrade
org.docx4j:docx4j-coreto 11.5.14 or later.