How severe is CVE-2020-5280?

CVE-2020-5280 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2020-5280?

CVE-2020-5280 affects the following packages: org.http4s:http4s-server_2.12 (Maven), org.http4s:http4s-server_2.12 (Maven), org.http4s:http4s-server_2.12 (Maven). Ecosystems affected: Maven.

How do I fix CVE-2020-5280?

Update org.http4s:http4s-server_2.12 to 0.18.26 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-5280 is resolved across your whole dependency graph.

How do I detect CVE-2020-5280 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.http4s:http4s-server_2.12, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2020-5280 if there is no patch (or I can't update yet)?

Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Is CVE-2020-5280 actively exploited in the wild?

No public exploit code has been indexed for CVE-2020-5280 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2020-5280?

CVE-2020-5280 has an EPSS (Exploit Prediction Scoring System) score of 7.0%, placing it in the 94th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2020-5280?

CVE-2020-5280 is classified as CWE-23 (CWE-23), Path Traversal (CWE-22). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2020-5280 published, and has it been updated?

CVE-2020-5280 was published on March 25, 2020 and was last updated on October 20, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

HIGH severity

CVE-2020-5280 — http4s-server_2.12

HIGHFix: http4s/http4s@250afdd

CVE-2020-5280 is a high-severity (CVSS 7.5) CWE-23 vulnerability in org.http4s:http4s-server_2.12. A fix is available for org.http4s:http4s-server_2.12 — see the affected versions and patch details below.

Local file inclusion vulnerability in http4s

Also known asGHSA-66q9-f7ff-mmx6

Published

Mar 25, 2020

Updated

Oct 20, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

None indexed

Exploitation data as of Oct 29, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

7.0%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs94th percentile — riskier than 94% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2020-5280 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 398,142 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

3 pkgs affected

☕org.http4s:http4s-server_2.12☕org.http4s:http4s-server_2.12☕org.http4s:http4s-server_2.12

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Impact

This vulnerability applies to all users of:

org.http4s.server.staticcontent.FileService
org.http4s.server.staticcontent.ResourceService
org.http4s.server.staticcontent.WebjarService

Path escaping

URI normalization is applied incorrectly. Requests whose path info contain ../ or // can expose resources outside of the configured location. Specifically:

FileService may expose any file on the local file system.
ResourceService may expose any resource on the class path.

Prefix matching

When the service is configured with a non-empty pathPrefix that doesn't end in a slash, any directories whose names are a prefix of systemPath (from FileService) or pathPrefix (from ResourceService) are exposed. For example, if pathPrefix is /foo and systemPath is /bar, a request to /foobaz/quux.txt exposes file /barbaz/quux.txt, when only files beneath /bar should be available.

URI decoding

URI segments are not decoded before resource resolution. This causes resources with reserved characters in their name to incorrectly return a 404. It also may incorrectly expose the rare resource whose name is URI encoded. This applies to FileService, ResourceService, and WebjarService.

Patches

In all three services, paths with an empty segment, a . segment, or a .. segment are now rejected with a 400 Bad Request response. This fixes exposure outside the configured root. Many clients already eliminate dot segments according to the rules in RFC3986, Section 5.2.4. A middleware that does so at the server level may be considered if there is demand.

If pathInfo is non-empty, and does not begin with /, then a 404 response is generated. This fixes the prefix matching exposure.

All path segments are URI decoded before being passed to the file system or resource path. This allows resolution of resources with reserved characters in the name, and prevents incorrect exposure of resources whose names are themselves URI encoded.

Workarounds

The recommended course is to upgrade:

v0.18.26, binary compatible with the 0.18.x series
v0.20.20, binary compatible with the 0.20.x series
v0.21.2, binary compatible with the 0.21.x series

Note that 0.19.0 is a deprecated release and has never been supported.

If an upgrade is impossible:

Temporarily copy FileService.scala, ResourceService.scala, and WebjarService.scala from the appropriate release series into your project and recompile with that, changing the package name and reference in your application.
Users of a servlet backend can use the servlet container's file serving capabilities.

Credits

Thank you to Thomas Gøytil for the discovery, responsible disclosure, and assistance testing of this vulnerability.

For more information

If you have any questions or comments about this advisory:

Open an issue in http4s/http4s
Email a maintainer:
- Ross A. Baker

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.http4s:http4s-server_2.12`	all versions	0.18.26`org.http4s:http4s-server_2.12:0.18.26`
☕Maven	`org.http4s:http4s-server_2.12`	≥ 0.19.0&&< 0.20.20	0.20.20`org.http4s:http4s-server_2.12:0.20.20`
☕Maven	`org.http4s:http4s-server_2.12`	≥ 0.21.0&&< 0.21.2	0.21.2`org.http4s:http4s-server_2.12:0.21.2`

Affected Products

1 product · 3 configurations

Application

http4stypelevel

≥ 0.21.0 && < 0.21.2

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.http4s:http4s-server_2.12, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.http4s:http4s-server_2.12 to 0.18.26 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-5280 is resolved across your whole dependency graph.
Workarounds
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Frequently Asked Questions

### Impact This vulnerability applies to all users of: * `org.http4s.server.staticcontent.FileService` * `org.http4s.server.staticcontent.ResourceService` * `org.http4s.server.staticcontent.WebjarService` #### Path escaping URI normalization is applied incorrectly. Requests whose path info contain `../` or `//` can expose resources outside of the configured location. Specifically: * `FileService` may expose any file on the local file system. * `ResourceService` may expose any resource on the class path. #### Prefix matching When the service is configured with a non-empty `pathPrefix` t