Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember’s HTTP/1.1 parser accepts differing duplicate Content-Length headers and uses the last value instead of rejecting the message. When an Ember server is behind a keep-alive intermediary that selects a different occurrence, an unauthenticated attacker can create CL.CL request smuggling that bypasses front-end controls, captures a later user’s headers, or poisons a cache.
The shared client parser can also misframe responses from a malicious or compromised upstream when the client acts as a proxy for multiple downstream consumers. This issue is fixed in versions 0.23.35 and 1.0.0-M47.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
High
Difficult to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
None
No disruption
CVSS Vector v3.1
Weakness Type (CWE)
References 4
https://github.com/http4s/http4s/commit/24e8d34e3ea89f8f23e0053ec9944f6467e8086d
security-advisories@github.com
https://github.com/http4s/http4s/releases/tag/v0.23.35
security-advisories@github.com
https://github.com/http4s/http4s/releases/tag/v1.0.0-M47
security-advisories@github.com
https://github.com/http4s/http4s/security/advisories/GHSA-p83c-4wj9-p6w9
security-advisories@github.com