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GHSA-p9j2-gv94-2wf4
No affected components available
Impact
A rewrites() or redirects() rule that builds its external destination hostname from request-controlled input can be pointed at an arbitrary hostname, regardless of the rule's hostname suffix. For a rewrite, Next.js proxies the request to that arbitrary host and serves the response from the application's origin, leading to Server-Side Request forgery. A redirects() rule configured this way is vulnerable to an Open Redirect.
This affects any destination that puts a dynamic segment in the hostname, whether from the path:
// next.config.js
module.exports = {
async rewrites() {
return [
{
source: '/:tenant',
destination: 'https://:tenant.api.example.com',
},
]
},
}
or from a has capture:
// next.config.js
module.exports = {
async rewrites() {
return [
{
source: '/',
has: [{ type: 'query', key: 'region', value: '(?<region>.+)' }],
destination: 'https://:region.api.example.com',
},
]
},
}
Workarounds
If you cannot upgrade immediately, do not build the hostname of an external rewrites() or redirects() destination from user-controlled input. If a dynamic subdomain is required, constrain the value to hostname-safe characters: value: '(?<region>[a-z0-9-]+)'.
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. No user interaction is needed for the attacker to exploit this vulnerability.
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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