CVE-2021-41084 Response Splitting from unsanitized headers in http4s
Attackers can perform response splitting by injecting unsanitized user input into HTTP headers or status fields in http4s applications.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-41084?
CVE-2021-41084 is a high-severity vulnerability in http4s, published on 21 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
http4s is an open source scala interface for HTTP. In affected versions 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.name`å), Header values (`Header.value`), Status reason phrases (`Status.reason`), URI paths (`Uri.Path`), URI authority registered names (`URI.RegName`) (through 0.21). This issue has been resolved in versions 0.21.30, 0.22.5, 0.23.4, and 1.0.0-M27 perform the following. As a matter of practice http4s services and client applications should sanitize any user input in the aforementioned fields before returning a request or response to the backend. The carriage return, newline, and null characters are the most threatening.
Which versions are affected by CVE-2021-41084?
40 open source packages ship an affected version, including org.http4s:http4s-client_2.12, org.http4s:http4s-client_2.13 and org.http4s:http4s-client_3. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
org.http4s:http4s-client_2.12 Maven | All versions | 0.21.29 |
org.http4s:http4s-client_2.12 Maven | All versions | 0.21.29 |
org.http4s:http4s-client_2.12 Maven | From 0.22.0 | 0.22.5 |
org.http4s:http4s-client_2.12 Maven | From 0.22.0 | 0.22.5 |
org.http4s:http4s-client_2.12 Maven | From 0.23.0 | 0.23.4 |
org.http4s:http4s-client_2.12 Maven | From 0.23.0 | 0.23.4 |
34 more packages
org.http4s:http4s-client_2.13 Maven | All versions | 0.21.29 |
org.http4s:http4s-client_2.13 Maven | All versions | 0.21.29 |
org.http4s:http4s-client_2.13 Maven | From 0.22.0 | 0.22.5 |
org.http4s:http4s-client_2.13 Maven | From 0.22.0 | 0.22.5 |
org.http4s:http4s-client_2.13 Maven | From 0.23.0 | 0.23.4 |
org.http4s:http4s-client_2.13 Maven | From 0.23.0 | 0.23.4 |
org.http4s:http4s-client_3 Maven | All versions | 0.21.29 |
org.http4s:http4s-client_3 Maven | All versions | 0.21.29 |
org.http4s:http4s-client_3 Maven | From 0.22.0 | 0.22.5 |
org.http4s:http4s-client_3 Maven | From 0.22.0 | 0.22.5 |
org.http4s:http4s-client_3 Maven | From 0.23.0 | 0.23.4 |
org.http4s:http4s-client_3 Maven | From 0.23.0 | 0.23.4 |
org.http4s:http4s-server_2.10 Maven | All versions to 0.21.28 | None |
org.http4s:http4s-server_2.10 Maven | All versions to 0.21.28 | None |
org.http4s:http4s-server_2.11 Maven | All versions to 0.21.28 | None |
org.http4s:http4s-server_2.11 Maven | All versions to 0.21.28 | None |
org.http4s:http4s-server_2.12 Maven | All versions | 0.21.29 |
org.http4s:http4s-server_2.12 Maven | All versions | 0.21.29 |
org.http4s:http4s-server_2.12 Maven | From 0.22.0 | 0.22.5 |
org.http4s:http4s-server_2.12 Maven | From 0.22.0 | 0.22.5 |
org.http4s:http4s-server_2.12 Maven | From 0.23.0 | 0.23.4 |
org.http4s:http4s-server_2.12 Maven | From 0.23.0 | 0.23.4 |
org.http4s:http4s-server_2.13 Maven | All versions | 0.21.29 |
org.http4s:http4s-server_2.13 Maven | All versions | 0.21.29 |
org.http4s:http4s-server_2.13 Maven | From 0.22.0 | 0.22.5 |
org.http4s:http4s-server_2.13 Maven | From 0.22.0 | 0.22.5 |
org.http4s:http4s-server_2.13 Maven | From 0.23.0 | 0.23.4 |
org.http4s:http4s-server_2.13 Maven | From 0.23.0 | 0.23.4 |
org.http4s:http4s-server_2.13.0-M5 Maven | All versions to 0.21.28 | None |
org.http4s:http4s-server_2.13.0-M5 Maven | All versions to 0.21.28 | None |
org.http4s:http4s-server_3 Maven | From 0.22.0 | 0.22.5 |
org.http4s:http4s-server_3 Maven | From 0.22.0 | 0.22.5 |
org.http4s:http4s-server_3 Maven | From 0.23.0 | 0.23.4 |
org.http4s:http4s-server_3 Maven | From 0.23.0 | 0.23.4 |
Products include Typelevel Http4s.
How do I fix CVE-2021-41084?
Upgrade org.http4s:http4s-client_2.12 to a fixed version for your release line: 0.21.29, 0.22.5 or 0.23.4.
Is CVE-2021-41084 being exploited?
There is no known exploitation of CVE-2021-41084 in the wild and no public exploit code.
Other vulnerabilities in http4s
- CVE-2021-39185 Default CORS config allows any origin with credentials
- CVE-2020-5280 Local file inclusion vulnerability in http4s
- CVE-2023-22465 Http4s has fatal error parsing User-Agent and Server headers
- CVE-2021-21294 Unbounded connection acceptance in http4s-blaze-server
- CVE-2025-59822 Http4s vulnerable to HTTP Request Smuggling due to improper handling of HTTP trailer section
Sources
Also known as GHSA-5vcm-3xc3-w7x3.