Impact
Undici clears Authorization headers on cross-origin redirects, but does not clear Cookie headers. By design, cookie headers are forbidden request headers, disallowing them to be set in RequestInit.headers in browser environments. Since Undici handles headers more liberally than the specification, there was a disconnect from the assumptions the spec made, and Undici's implementation of fetch.
As such this may lead to accidental leakage of cookie to a 3rd-party site or a malicious attacker who can control the redirection target (ie. an open redirector) to leak the cookie to the 3rd party site.
Patches
This was patched in e041de359221ebeae04c469e8aff4145764e6d76, which is included in version 5.26.2.
References
ranjit-git Reporter
KhafraDev Remediation developer
mcollina Coordinator
Impact
Undici clears Authorization headers on cross-origin redirects, but does not clear
Cookieheaders. By design,cookieheaders are forbidden request headers, disallowing them to be set inRequestInit.headersin browser environments. Since Undici handles headers more liberally than the specification, there was a disconnect from the assumptions the spec made, and Undici's implementation of fetch.As such this may lead to accidental leakage of cookie to a 3rd-party site or a malicious attacker who can control the redirection target (ie. an open redirector) to leak the cookie to the 3rd party site.
Patches
This was patched in e041de359221ebeae04c469e8aff4145764e6d76, which is included in version 5.26.2.
References