Critical

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

Disclosed: 30.03.2020
Updated: 11.10.2026 12:22

Vulnerability

Micronaut's HTTP client is vulnerable to "HTTP Request Header Injection" due to not validating request headers passed to the client.

Example of vulnerable code:

java

@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)
        );
    }
}

In the above case a query value received from a user is passed as a header value to the client. Since the client doesn't validate the header value the request headers and body have the potential to be manipulated.

For example, a user that supplies the following payload, can force the client to make multiple attacker-controlled HTTP requests.

java

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);

Note that using @HeaderValue instead of @QueryValue is not vulnerable since Micronaut's HTTP server does validate the headers passed to the server, so the exploit can only be triggered by using user data that is not an HTTP header (query values, form data etc.).

Impact

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.

Patches

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

Workarounds

Do not pass user data directly received from HTTP request parameters as headers in the HTTP client.

References

Fix commits

For more information

If you have any questions or comments about this advisory:

Open an issue in micronaut-core
Email us at info@micronaut.io

Credit

Originally reported by @JLLeitschuh

Affected software

Click a technology to see all vulnerabilities affecting it.

Platform	Package	Vulnerable versions	Fixed in
Java / Kotlin (Maven)	io.micronaut:micronaut-http-client	< 1.2.11, >= 1.3.0, < 1.3.2	1.2.11, 1.3.2

References

CVSS score 9.8/10

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): CWE-444
Platform: Java / Kotlin (Maven)
Package: io.micronaut:micronaut-http-client
Disclosed: 30.03.2020
Updated: 11.10.2026 12:22

Sources and licenses

OSV / GitHub Advisory Database - GHSA-694p-xrhg-x3wm - CC BY 4.0

Vulnerability history: io.micronaut:micronaut-http-client

All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.

Total entries: 3
First → latest: 03.2020 07.2026
Without a fix: 0
Exploited in attacks: 0

Severity breakdown

Critical 1
High 1
Medium 1

Disclosures per year

2020: 1
2021: 0
2022: 0
2023: 0
2024: 0
2025: 0
2026: 2

09.07.2026

Micronaut: DefaultHttpClient follows redirects, forwarding Authorization, Cookie, and Proxy-Authorization headers

Medium · 6.8 ghsa-q6gh-6v2r-hjv3 >= 1.2.8, < 3.10.6, >= 4.0.0-M1, < 4.10.24, >= 5.0.0-M1, < 5.0.1 3.10.6, 4.10.24, 5.0.1
09.07.2026

Micronaut doesn't set a maximum redirect count for its HTTP Client, enabling infinite loop DoS

High · 7.5 ghsa-387m-935m-c4vw < 3.10.7, >= 4.0.0-M1, < 4.10.24, >= 5.0.0-M1, < 5.0.1 3.10.7, 4.10.24, 5.0.1
30.03.2020

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

Critical · 9.8 CVE-2020-7611 < 1.2.11, >= 1.3.0, < 1.3.2 1.2.11, 1.3.2

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

Vulnerability

Impact

Patches

Workarounds

References

For more information

Credit

Affected software

References

Vulnerability history: io.micronaut:micronaut-http-client

Severity breakdown

Disclosures per year

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