Response Splitting from unsanitized headers
Published Sep 21, 2021 · Updated Nov 3, 2026
Original summary
Normalized public record · Updated Nov 3, 2026
Response Splitting from unsanitized headers
Publisher and source text is retained separately from QFinch interpretation.
QFinch assessment
http4s is vulnerable to response-splitting or request-splitting attacks when untrusted user input is used to create any of the following fields:
Potential impact
http4s is vulnerable to response-splitting or request-splitting attacks when untrusted user input is used to create any of the following fields: Header names (Header.nameå Header values (Header.value) Status reason phrases (Status.reason) URI paths (Uri.Path) URI authority registered names (URI.RegName) (through 0.21) The following backends render invalid carriage return, newline, or null characters in an unsafe fashion. | | blaze-server | ember-server | blaze-client | ember-client | jetty-client | |:---------------|:-------------|:-------------|:-------------|--------------|--------------| | header names | ⚠ | ⚠ | ⚠ | ⚠ | ⚠ | | header values | ⚠ | ⚠ | ⚠ | ⚠ | | | status reasons | ⚠ | ⚠ | | | | | URI paths | | | ⚠ | ⚠ | | | URI regnames | | | ⚠ < 0.22 | ⚠ < 0.22 | | For example, given the following service: A clean author parameter returns a clean response: A malicious author parameter allows a user-agent to hijack the response from our server and return different content:
Evidence: public source recordsAffected products
| Affected package, product or range | Fix status |
|---|---|
| Consult the referenced vendor advisory for affected versions. | Consult source advisory |
Matching a version is only one part of assessing exposure. QFinch has not assessed your environment on this public page.
Remediation
Apply the vendor-supported fixed release or mitigation, then verify the affected component is no longer reachable.
- Confirm the affected product and reachable code path exist in your environment.
- Apply the vendor-supported patch or mitigation from the primary advisory.
- Rescan the exact deployed revision and retain verification evidence.
Evidence coverage
- SSVC priority
- MEDIUM
- Confidence
- Not available
- Aliases
- None reported
Scores appear only when corresponding evidence exists. Missing data is never interpreted as zero risk.
Sources and record history
Record history
Published Sep 21, 2021 · Last refreshed Nov 3, 2026