# CVE-2026-91863: Apache Neethi stack exhaustion via deeply nested WS-Policy elements

Source: https://junglewise.ai/threats/cve-2026-91863-a-specially-crafted-ws-policy-document-with-deeply-nested-policy  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-21. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-91863 · Severity: high · CVSS 7.5 · Published 2026-09-21

Apache Neethi is a library that processes WS-Policy documents used in web services. An attacker can craft a specially designed WS-Policy file with deeply nested elements that bypasses the parser's safety checks, causing the application to crash by exhausting available thread stack memory. This results in a denial of service, making services unavailable.

Technologies: [Apache Neethi](https://junglewise.ai/threats/technologies/apache-neethi). Vendors: [Apache](https://junglewise.ai/threats/vendors/apache).

## Quick answers

**Is CVE-2026-91863 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-91863 being exploited in the wild.

**How severe is CVE-2026-91863?** High severity, with a CVSS score of 7.5, published 21 September 2026.

**Which products and versions are affected?** Apache Neethi before 3.2.4.

**Is there a fix for CVE-2026-91863?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-91863 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-91863?** Check whether you run Apache Neethi at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability exists in Neethi's WS-Policy parser, which fails to properly enforce its nesting-depth limit when processing maliciously crafted policy documents. An attacker can send a specially constructed WS-Policy XML document that triggers recursive parsing without hitting the depth limit, leading to stack exhaustion and parser crash. This is a network-accessible denial of service affecting applications using Neethi versions before 3.2.4.

## Affected products

- Apache Neethi before 3.2.4

## Timeline

- 2026-09-21: disclosed

## References

- [https://repo.maven.apache.org/maven2](https://repo.maven.apache.org/maven2)
- [https://lists.apache.org/thread/72kxj71lvrqqx90xxqqctvpbw0t8mpxw](https://lists.apache.org/thread/72kxj71lvrqqx90xxqqctvpbw0t8mpxw)

## Related threats

- [Neethi remote policy fetch thread exhaustion](https://junglewise.ai/threats/cve-2026-91867-when-neethi-fetches-a-remote-policy-reference-it-only-limits-the)
- [Apache Neethi policy intersection exponential complexity denial of service](https://junglewise.ai/threats/cve-2026-91866-a-specially-crafted-pair-of-ws-policy-documents-can-force-neethi)
- [Apache Neethi exponential policy expansion denial of service](https://junglewise.ai/threats/cve-2026-91865-a-small-ws-policy-document-using-repeated-policy-references-can)
- [Apache Neethi heap exhaustion in WS-Policy processing](https://junglewise.ai/threats/cve-2026-91864-a-specially-crafted-ws-policy-document-can-pack-unlimited-content)
- [Apache Neethi does not impose any restrictions on URIs when manually fetching remote policy references through the…](https://junglewise.ai/threats/cve-2026-42404-apache-neethi-doesn-t-impose-any-restrictions-on-uris-when)