Summary
Http4s: ResourceService and Webjar Service path escape via percent-encoded separators
The static content handlers ResourceService and WebjarService URL decode each path segment and then reject only segments that are exactly "", ".", or "..". A percent-encoded separator (%2F) lets an attacker smuggle a ../ segment past that filter and escape the configured base, reading resources that should not be public.
On Windows, a similar attack exists with (%5C).
Preconditions
- Application uses
ResourceService(with a non-root base path) orWebjarService - At least one classpath entry is served from a directory (e.g.
sbt run, exploded .war) - Backend forwards
%2F/%5Cwithout normalizing (e.g., Ember, Blaze)
Fixes
The patch rejects any decoded path segment containing / (%2F) or \ (%5C) with a 400 Bad Request in ResourceService and WebjarService.
FileService was not exploitable, but the same guards are applied for consistency and to remove its reliance on path normalization.
Workarounds
- Deploy as a fat jar, with no filesystem directories on the classpath.
- Front the service with a proxy that rejects/normalizes
%2Fand%5Cin the request path.
Impact
Disclosure of classpath or webjar resources outside the configured base.
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-2026-69201 has a CVSS score of 5.9 (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 (0.23.35, 1.0.0-M47); 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.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
org.http4s:http4s-server_2.12 to 0.23.35 or later; org.http4s:http4s-server_2.13 to 0.23.35 or later; org.http4s:http4s-server_3 to 0.23.35 or later; org.http4s:http4s-server_3 to 1.0.0-M47 or later; org.http4s:http4s-server_2.13 to 1.0.0-M47 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-69201? CVE-2026-69201 is a medium-severity path traversal vulnerability in org.http4s:http4s-server_2.12 (maven), affecting versions <= 0.23.34. It is fixed in 0.23.35, 1.0.0-M47. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
- How severe is CVE-2026-69201? CVE-2026-69201 has a CVSS score of 5.9 (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 packages are affected by CVE-2026-69201?
org.http4s:http4s-server_2.12(maven) (versions <= 0.23.34)org.http4s:http4s-server_2.13(maven) (versions <= 0.23.34)org.http4s:http4s-server_3(maven) (versions <= 0.23.34)
- Is there a fix for CVE-2026-69201? Yes. CVE-2026-69201 is fixed in 0.23.35, 1.0.0-M47. Upgrade to this version or later.
- Is CVE-2026-69201 exploitable, and should I be worried? Whether CVE-2026-69201 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-2026-69201 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-2026-69201?
- Upgrade
org.http4s:http4s-server_2.12to 0.23.35 or later - Upgrade
org.http4s:http4s-server_2.13to 0.23.35 or later - Upgrade
org.http4s:http4s-server_3to 0.23.35 or later - Upgrade
org.http4s:http4s-server_3to 1.0.0-M47 or later - Upgrade
org.http4s:http4s-server_2.13to 1.0.0-M47 or later
- Upgrade