What’s Vulnerable › Vulnerabilities

CVE-2021-39185: Default CORS config allows any origin with credentials

• Severity: medium (CVSS 6.4 v2.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-09-01 · updated 2026-06-17
• Weakness: CWE-346

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.

Affected products

• http4s: through 0.21.26; from 0.22.0 through 0.22.2; 0.23.0, 0.23.1, 1.0.0-milestone1, 1.0.0-milestone10, 1.0.0-milestone11, 1.0.0-milestone12 (+20)

References

• https://github.com/http4s/http4s/releases/tag/v0.23.2
• https://github.com/http4s/http4s/security/advisories/GHSA-52cf-226f-rhr6
• https://github.com/http4s/http4s/releases/tag/v0.23.2
• https://github.com/http4s/http4s/security/advisories/GHSA-52cf-226f-rhr6

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