Summary
StaticFile.fromUrl can leak presence of a directory
Workarounds
Don't call StaticFile.fromUrl with non-file URLs.
For more information
If you have any questions or comments about this advisory:
- Open an issue in the http4s repository
- Disclose further vulnerabilities according to the http4s security policy
Impact
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
- 1.0.0-M1 through 1.0.0-M22
Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.
CVE-2021-32643 has a CVSS score of 5.8 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.21.24, 0.22.0-RC1, 0.23.0-RC1, 1.0.0-M23); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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The patch is available in the following versions:
- v0.21.24
- v0.22.0-RC1
- v0.23.0-RC1
- v1.0.0-M23
Note: a previous version of this advisory incorrectly referred to 0.22.0-M9 and 0.23.0-M2.
Frequently Asked Questions
- What is CVE-2021-32643? CVE-2021-32643 is a medium-severity path traversal vulnerability in org.http4s:http4s-core (maven), affecting versions >= 0.21.7, < 0.21.24. It is fixed in 0.21.24, 0.22.0-RC1, 0.23.0-RC1, 1.0.0-M23. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
- How severe is CVE-2021-32643? CVE-2021-32643 has a CVSS score of 5.8 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of org.http4s:http4s-core are affected by CVE-2021-32643? org.http4s:http4s-core (maven) versions >= 0.21.7, < 0.21.24 is affected.
- Is there a fix for CVE-2021-32643? Yes. CVE-2021-32643 is fixed in 0.21.24, 0.22.0-RC1, 0.23.0-RC1, 1.0.0-M23. Upgrade to this version or later.
- Is CVE-2021-32643 exploitable, and should I be worried? Whether CVE-2021-32643 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2021-32643 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2021-32643?
- Upgrade
org.http4s:http4s-coreto 0.21.24 or later - Upgrade
org.http4s:http4s-coreto 0.22.0-RC1 or later - Upgrade
org.http4s:http4s-coreto 0.23.0-RC1 or later - Upgrade
org.http4s:http4s-coreto 1.0.0-M23 or later
- Upgrade