# CVE-2026-107937: Apache CXF multipart MTOM header size limit bypass

Source: https://junglewise.ai/threats/cve-2026-107937-in-apache-cxf-the-parser-for-multipart-mtom-attachment-part  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-09. Updated: 2026-10-16  
License: CC BY 4.0 with a link back

CVE-2026-107937 · Severity: high · CVSS 7.5 · Published 2026-10-09

Apache CXF is a web services framework that processes SOAP and REST messages. The MTOM (Message Transmission Optimization Mechanism) parser failed to properly enforce limits on attachment header sizes and counts, allowing an attacker to send specially crafted requests that consume unbounded memory on the server, resulting in denial of service.

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

## Quick answers

**Is CVE-2026-107937 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-107937 being exploited in the wild.

**How severe is CVE-2026-107937?** High severity, with a CVSS score of 7.5, published 9 October 2026.

**Which products and versions are affected?** Apache CXF prior to 4.2.4, 4.1.9, and 3.6.13.

**Is there a fix for CVE-2026-107937?** Yes: fixed in Apache CXF 4.2.4, 4.1.9, 3.6.13. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-107937 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-107937?** Check whether you run Apache CXF 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.

## How to fix

- Fixed in Apache CXF 4.2.4, 4.1.9, 3.6.13

## Technical details

The multipart/MTOM header parser in Apache CXF does not fully enforce the attachment-max-header-size and attachment-headers-max-count configuration limits. Size limits are applied per physical line rather than across folded header values or repeated headers, and count limits check distinct header names instead of total header lines. An unauthenticated remote attacker can send multipart requests with large folded or repeated headers, causing the server to allocate unbounded memory.

## Affected products

- Apache CXF prior to 4.2.4, 4.1.9, and 3.6.13

## Timeline

- 2026-10-09: disclosed

## References

- [https://repo.maven.apache.org/maven2](https://repo.maven.apache.org/maven2)
- [https://lists.apache.org/thread.html/x9twtpv3d04qj83t6w9xkh9y2q28zztj](https://lists.apache.org/thread.html/x9twtpv3d04qj83t6w9xkh9y2q28zztj)

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