9.1 High
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
7.3 High
AI Score
Confidence
High
0.0004 Low
EPSS
Percentile
8.8%
Some specifically configured Spin applications that use self
requests without a specified URL authority can be induced to make requests to arbitrary hosts via the Host
HTTP header.
If an application’s manifest contains a component with configuration such as
allowed_outbound_hosts = ["http://self", "https://self"]
and code such as
let res: Response = spin_sdk::http::send(
Request::new(Method::Get, "/") // Note: the request URI does not contain a URL authority
).await?;
Then that application can be induced to send an outgoing request to another host (leading the app to process the response assuming it comes from another component in the same application). This can be induced with a request such as
curl -H"Host: google.com:80" localhost:3000 # Assuming the application is served on localhost:3000
> Note: If using a SDK that does not use wasi:http/outgoing-handler
, the port can be omitted from the URL.
The following conditions need to be met for an application to be vulnerable:
Host
header, and leaves the Host
header set to the original value by the client.allowed_outbound_hosts
list containing "self"
.If all of these conditions apply, then Spin will use the inbound request’s Host
header to determine the authority
part of the URL if none is explicitly provided in the request’s URL.
Fermyon’s Fermyon Cloud serverless product and applications hosted on it are known not to be vulnerable.
Has the problem been patched? What versions should users upgrade to?
Spin version 2.4.3 is being released with this advisory going public.
For deployments of Spin, a workaround is to ensure that the Host
header is sanitized to match the application a request is routed to.
For individual applications, multiple workarounds exist:
Host
headerallowed_outbound_hosts
list instead of self
9.1 High
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
7.3 High
AI Score
Confidence
High
0.0004 Low
EPSS
Percentile
8.8%