CVE-2026-50645: Apache CXF denial of service via attachment headers

Executive brief

Apache CXF, a framework used to build and develop web services, contains a flaw in how it handles message attachments. An attacker can send a specially crafted message with an excessive number of attachment headers, causing the system to consume all available resources. This can lead to a denial-of-service, making the web service unavailable to legitimate users and potentially impacting business operations.

Technical details

A resource exhaustion vulnerability (CWE-400) exists in Apache CXF's core deserialization logic. The component does not impose a limit on the number of attachment headers processed per message. A remote, unauthenticated attacker can exploit this by sending a message with a large number of headers, leading to uncontrolled memory or CPU consumption and a Denial of Service (DoS) condition. The issue is resolved in versions 4.2.2 and 4.1.7 by implementing a default limit of 500 attachments per message.

Affected products

• Apache cxf-core >= 4.2.0, < 4.2.2; < 4.1.7

Timeline

• 2026-06-11: disclosed: Initial disclosure on oss-security list
• 2026-06-12: advisory: GitHub Advisory published
• 2026-06-12: patched: Patched versions 4.2.2 and 4.1.7 released

References

• https://api.github.com/users/julianladisch
• https://github.com/julianladisch
• https://api.github.com/users/julianladisch/gists%7B/gist_id%7D
• https://api.github.com/users/julianladisch/repos
• https://avatars.githubusercontent.com/u/533612?v=4
• https://api.github.com/users/julianladisch/events%7B/privacy%7D