http_protocol.c in (1) IBM HTTP Server 6.0 before 6.0.2.13 and 6.1 before 6.1.0.1, and (2) Apache HTTP Server 1.3 before 1.3.35, 2.0 before 2.0.58, and 2.2 before 2.2.2, does not sanitize the Expect header from an HTTP request when it is reflected back in an error message, which might allow cross-site scripting (XSS) style attacks using web client components that can send arbitrary headers in requests, as demonstrated using a Flash SWF file.
Use CWE-79, Apache vendor hub and Http Server product page to widen CVE-2006-3918 into its surrounding weakness, vendor, and product context.
Compare it with CVE-2025-23048, CVE-2025-58098 and CVE-2025-59775 for nearby disclosures in the same product family.