CVE-2026-107937 Denial of service in Apache CXF

High 7.5 Published 9 Oct 2026 Updated 15 Oct 2026

Remote attackers can cause denial of service via memory exhaustion by bypassing attachment header limits in Apache CXF.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2026-107937?

CVE-2026-107937 is a high-severity denial of service vulnerability in Apache Cxf, published on 9 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

In Apache CXF, the parser for multipart/MTOM attachment part headers did not fully enforce the configured attachment-max-header-size (default 300 characters) and attachment-headers-max-count (default 500) limits. The size limit was applied only to each physical line, not to a header value built from continuation lines or to the combined values of a repeated header. The count limit was checked against the number of distinct header names, not the total number of header lines. A remote, unauthenticated attacker could send a multipart request with very large folded or repeated part headers. The server would then allocate memory without bound, causing a denial of service. Users are recommended to upgrade to versions 4.2.4 or 4.1.9 or 3.6.13, which fix this issue.

Weakness: CWE-770

Which versions are affected by CVE-2026-107937?

It affects 1 product.

Products include Apache Cxf.

How do I fix CVE-2026-107937?

Upgrade to a fixed version.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-107937 being exploited?

There is no known exploitation of CVE-2026-107937 in the wild and no public exploit code.

All Apache Cxf vulnerabilities

Sources

Also known as CLEANSTART-2026-RF61847, GHSA-7cpr-66jm-x98h.