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GHSA-6v7p-v754-j89v
No affected components available
Vulnerability
Styx is vulnerable to CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting').
Vulnerable Component
The vulnerable component is the com.hotels.styx.api.HttpHeaders.Builder due to disabling the HTTP Header validation built into Netty in these locations:
https://github.com/HotelsDotCom/styx/blob/e1d578e9b9c38df9cd19c21dc2eb9b949d85b558/components/api/src/main/java/com/hotels/styx/api/HttpHeaders.java#L145
https://github.com/HotelsDotCom/styx/blob/e1d578e9b9c38df9cd19c21dc2eb9b949d85b558/components/api/src/main/java/com/hotels/styx/api/HttpHeaders.java#L145
new DefaultHttpHeaders(false) disables the built-in validation in Netty. Either use the default constructor or new DefaultHttpHeaders(true instead.
Additionally, another vulnerable component is the StyxToNettyResponseTranslator due to also disabling the HTTP Header validation built into netty in this location.
https://github.com/HotelsDotCom/styx/blob/8d60e5493e65d0d536afc0b350dcb02d24e0f7a7/components/server/src/main/java/com/hotels/styx/server/netty/connectors/StyxToNettyResponseTranslator.java#L30
DefaultHttpResponse nettyResponse = new DefaultHttpResponse(version, httpResponseStatus, false);
new DefaultHttpResponse(version, httpResponseStatus, false); disables the built-in validation in Netty. Please use the constructor new DefaultHttpResponse(version, httpResponseStatus, true);
Proof of Concept
The following test plugin proves that there is no header validation occurring.
static class VulnerablePlugin implements Plugin {
@Override
public Eventual<LiveHttpResponse> intercept(LiveHttpRequest request, Chain chain) {
String header = request.queryParam("header-value").get();
LiveHttpRequest newRequest = request.newBuilder()
.header("myRequestHeader", header)
.build();
return chain.proceed(newRequest).map(response ->
response.newBuilder().header("myResponseHeader", header).build()
) ;
}
}
@Test
public void simpleHeaderInjectionVulnerabilityPOC() {
Plugin vulnerablePlugin = new VulnerablePlugin();
// a simple way to mock the downstream system
HttpInterceptor.Chain chain = request -> {
assertThat(request.header("myRequestHeader").orElse(null), is("test\r\nAnother: CRLF_Injection"));
return Eventual.of(response(OK).build());
};
// an example request you expect your plugin to receive
String encodedGet = URLEncoder.encode("test\r\nAnother: CRLF_Injection");
LiveHttpRequest request = get("/foo?header-value=" + encodedGet)
.build();
// since this is a test, we want to wait for the response
LiveHttpResponse response = Mono.from(vulnerablePlugin.intercept(request, chain)).block();
assertThat(response.header("myResponseHeader").orElse(null), is("test\r\nAnother: CRLF_Injection"));
}
Additionally, if you run this LiveHttpResponse from this test through the StyxToNettyResponseTranslator::toNettyResponse, ideally, it would have caused an exception to be thrown. In its current state, it does not.
Similar Vulnerabilities
There have been reports of similar vulnerabilities in other popular libraries.
GHSA-35fr-h7jr-hh86 -> CVE-2019-16771 GHSA-mvqp-q37c-wf9j -> CVE-2019-17513
Finding
This vulnerability was found due to this query that Jonathan Leitschuh contributed to the Semmle QL project. https://lgtm.com/rules/1510696449842/alerts/
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The impact is confined to the system where the vulnerability exists. There is a high impact on the integrity of the data.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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