[GHSA-cjpg-rgq5-fr37] Spring Framework Multipart Request Smuggling in Spring MVC and WebFlux - #9588
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September 16, 2026 17:25
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The affected package should be
org.springframework:spring-core, notspring-webmvc/spring-webflux.The fix for CVE-2026-41853 is commit 8a93a889620c ("Fix parsing failure for MIME types with quoted pairs", gh-36730), a one-line change to
MimeTypeUtils.parseMimeTypeInternalinspring-core: the parameter scanner toggled itsquotedstate on backslash-escaped quotes, so a\"inside a quoted parameter value (e.g. the multipartboundary) ended the quoted string early and a following;was treated as a parameter separator. That is the interpretation gap a WAF/proxy and the application disagree on (CWE-444).Diffing
v6.2.18...v6.2.19shows no production change underspring-webmvc/orspring-webflux/related to this issue; thespring-webmultipart codec changes in that release are commit a58fdeaf3fc1 (gh-36694), an unrelatedPartGeneratortemp-file race fix.MimeTypeUtilsis present only in thespring-corejar (Spring publishes thin per-module jars), and the vulnerable line is present in spring-core at v5.3.39 / v6.1.21 / v6.2.18 / v7.0.7 and fixed at v6.2.19 / v7.0.8.