CVE-2026-107937: Apache CXF: The attachment header size and count limits can be bypassed, which allows denial of service through memory exhaustion.

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-09 · updated 2026-10-16
Weakness: CWE-770

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.

Affected products

Apache Software Foundation Apache CXF: before 3.6.13; from 4.0.0 before 4.1.9; from 4.2.0 before 4.2.4 — fixed in 3.6.13, 4.1.9, 4.2.4

How to fix

Upgrade to a fixed version: Apache Software Foundation Apache CXF 3.6.13, 4.1.9, 4.2.4. Check the vendor advisory for mitigations.

References

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