Affected versions of http-signature contain a vulnerability which can allow an attacker in a privileged network position to modify header names and change the meaning of the request, without requiring an updated signature.

This problem occurs because vulnerable versions of http-signature sign the contents of headers, but not the header names.

Proof of Concept

Consider this to be the initial, untampered request: http POST /pay HTTP/1.1 Host: example.com Date: Thu, 05 Jan 2012 21:31:40 GMT X-Payment-Source: src@money.com X-Payment-Destination: dst@money.com Authorization: Signature keyId="Test",algorithm="rsa-sha256",headers="x-payment-source x-payment-destination" MDyO5tSvin5...

And the request is intercepted and tampered as follows: http X-Payment-Source: dst@money.com // Emails switched X-Payment-Destination: src@money.com Authorization: Signature keyId="Test",algorithm="rsa-sha256",headers="x-payment-destination x-payment-source" MDyO5tSvin5...

In the resulting responses, both requests would pass signature verification without issue. src@money.com\n dst@money.com\n

Recommendation

Update to version 0.10.0 or higher.