CVE-2021-32643: Http4s is a Scala interface for HTTP services. `StaticFile.fromUrl` can leak the presence of a directory on a server when the `URL` scheme is not `fil...

Description

Http4s is a Scala interface for HTTP services. `StaticFile.fromUrl` can leak the presence of a directory on a server when the `URL` scheme is not `file://`, and the URL points to a fetchable resource under its scheme and authority. The function returns `F[None]`, indicating no resource, if `url.getFile` is a directory, without first checking the scheme or authority of the URL. If a URL connection to the scheme and URL would return a stream, and the path in the URL exists as a directory on the server, the presence of the directory on the server could be inferred from the 404 response. The contents and other metadata about the directory are not exposed. This affects http4s versions: 0.21.7 through 0.21.23, 0.22.0-M1 through 0.22.0-M8, 0.23.0-M1, and 1.0.0-M1 through 1.0.0-M22. The [patch](https://github.com/http4s/http4s/commit/52e1890665410b4385e37b96bc49c5e3c708e4e9) is available in the following versions: v0.21.24, v0.22.0-M9, v0.23.0-M2, v1.0.0-M23. As a workaround users can avoid calling `StaticFile.fromUrl` with non-file URLs.

Metrics

CVSS 3.1

5.8/10

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

EPSS Probability

1.40%

68.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions	Update
Typelevel	Http4s	>= 0.21.7, < 0.21.24	—
Typelevel	Http4s	0.22.0	Milestone1
Typelevel	Http4s	0.23.0	Milestone1
Typelevel	Http4s	1.0.0	Milestone1

References

https://github.com/http4s/http4s/commit/52e1890665410b4385e37b96bc49c5e3c708e4e9Patch, Third Party Advisory
https://github.com/http4s/http4s/security/advisories/GHSA-6h7w-fc84-x7p6Patch, Third Party Advisory
https://mvnrepository.com/artifact/org.http4s/http4s-coreThird Party Advisory
https://github.com/http4s/http4s/commit/52e1890665410b4385e37b96bc49c5e3c708e4e9Patch, Third Party Advisory
https://github.com/http4s/http4s/security/advisories/GHSA-6h7w-fc84-x7p6Patch, Third Party Advisory
https://mvnrepository.com/artifact/org.http4s/http4s-coreThird Party Advisory

Timeline

Published: May 27, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-32643?

Http4s is a Scala interface for HTTP services. `StaticFile.fromUrl` can leak the presence of a directory on a server when the `URL` scheme is not `file://`, and the URL points to a fetchable resource under its scheme and authority. The function returns `F[None]`, indicating no resource, if `url.getFile` is a directory, without first checking the scheme or authority of the URL. If a URL connection to the scheme and URL would return a stream, and the path in the URL exists as a directory on the server, the presence of the directory on the server could be inferred from the 404 response. The contents and other metadata about the directory are not exposed. This affects http4s versions: 0.21.7 through 0.21.23, 0.22.0-M1 through 0.22.0-M8, 0.23.0-M1, and 1.0.0-M1 through 1.0.0-M22. The [patch](https://github.com/http4s/http4s/commit/52e1890665410b4385e37b96bc49c5e3c708e4e9) is available in the following versions: v0.21.24, v0.22.0-M9, v0.23.0-M2, v1.0.0-M23. As a workaround users can avoid calling `StaticFile.fromUrl` with non-file URLs.

How severe is CVE-2021-32643?

CVE-2021-32643 has a CVSS score of 5.8/10 (MEDIUM severity). The EPSS model estimates a 1.40% probability of exploitation in the next 30 days.

How do I fix CVE-2021-32643?

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.