CVE-2026-69201 Http4s: ResourceService and Webjar Service path escape via percent-encoded separators

What is CVE-2026-69201?

CVE-2026-69201 is a medium-severity path traversal vulnerability in http4s, published on 15 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, ResourceService and WebjarService decode each URL path segment but reject only segments exactly equal to an empty string, a dot, or two dots. A request containing percent-encoded slash or backslash separators can turn an accepted segment into a parent-directory traversal after decoding, allowing access to classpath or WebJar resources outside the configured base when a directory-backed classpath is served and the backend preserves the encoded separator. The patch rejects decoded segments containing slash or backslash in ResourceService and WebjarService, and applies the same guard to the non-exploitable FileService for consistency. This issue is fixed in versions 0.23.35 and 1.0.0-M47.

Weakness: CWE-22

Which versions are affected by CVE-2026-69201?

10 open source packages ship an affected version, including org.http4s:http4s-server_2.13, org.http4s:http4s-server_2.12 and org.http4s:http4s-server_3.

How do I fix CVE-2026-69201?

Upgrade org.http4s:http4s-server_2.13 to a fixed version for your release line: 0.23.35 or 1.0.0-M47.

Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.

Is CVE-2026-69201 being exploited?

There is no known exploitation of CVE-2026-69201 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-crq5-92j2-j7wv.