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

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.

Source published

9 Oct 2026 10:19:53 UTC

Source modified

15 Oct 2026 17:45:25 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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