CVE-2021-39185

Name: CVE-2021-39185
Creator: NVD / NIST
Published: 2021-09-01T20:15:07.447+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.1/10EPSS 0.59%

Last modified Jun 17, 2026

CVE-2021-39185 is a critical-severity vulnerability rated 9.1/10 on the CVSS scale. Http4s is a minimal, idiomatic Scala interface for HTTP services. In http4s versions 0.21.26 and prior, 0.22.0 through 0.22.2, 0.23.0, 0.23.1, and 1.0.0-M1 through 1.0.0-M24, the default CORS configuration is vulnerable to an origin reflection attack. EPSS estimates a 0.59% chance of exploitation in the next 30 days.

Description

Http4s is a minimal, idiomatic Scala interface for HTTP services. In http4s versions 0.21.26 and prior, 0.22.0 through 0.22.2, 0.23.0, 0.23.1, and 1.0.0-M1 through 1.0.0-M24, the default CORS configuration is vulnerable to an origin reflection attack. The middleware is also susceptible to a Null Origin Attack. The problem is fixed in 0.21.27, 0.22.3, 0.23.2, and 1.0.0-M25. The original `CORS` implementation and `CORSConfig` are deprecated. See the GitHub GHSA for more information, including code examples and workarounds.

Metrics

CVSS 3.1

9.1/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS Probability

0.59%

43.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-346

Affected Software

Vendor	Product	Versions	Update
Typelevel	Http4s	<= 0.21.26	—
Typelevel	Http4s	>= 0.22.0, <= 0.22.2	—
Typelevel	Http4s	0.23.0	—
Typelevel	Http4s	0.23.1	—
Typelevel	Http4s	1.0.0	Milestone1

References

https://github.com/http4s/http4s/releases/tag/v0.23.2Third Party Advisory
https://github.com/http4s/http4s/security/advisories/GHSA-52cf-226f-rhr6Patch, Third Party Advisory
https://github.com/http4s/http4s/releases/tag/v0.23.2Third Party Advisory
https://github.com/http4s/http4s/security/advisories/GHSA-52cf-226f-rhr6Patch, Third Party Advisory

Timeline

Published: Sep 1, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-39185?

How severe is CVE-2021-39185?

CVE-2021-39185 has a CVSS score of 9.1/10 (CRITICAL severity). The EPSS model estimates a 0.59% probability of exploitation in the next 30 days.

How do I fix CVE-2021-39185?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-39185?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST