CVE-2026-63490 Handlebars.java: Arbitrary file read in `SpringTemplateLoader` via URL-fragment suffix bypass
An unauthenticated remote attacker can read arbitrary files accessible to the JVM by exploiting a path traversal vulnerability in the SpringTemplateLoader of Handlebars.java.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-63490?
CVE-2026-63490 is a high-severity path traversal vulnerability in jknack handlebars.java, published on 20 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Handlebars.java provides logic-less and semantic Mustache templates with Java. Prior to 4.5.3, com.github.jknack.handlebars.springmvc.SpringTemplateLoader resolves attacker-influenced Spring MVC view names through Spring ResourceLoader without the path-containment validation used by other URL-based loaders. In handlebars-springmvc/src/main/java/com/github/jknack/handlebars/springmvc/SpringTemplateLoader.java, a view name using a file: or classpath: URL and ending with the # fragment delimiter places the appended .hbs suffix in the fragment, which FileUrlResource.exists() and URL.openStream() discard. HandlebarsViewResolver in handlebars-springmvc/src/main/java/com/github/jknack/handlebars/springmvc/HandlebarsViewResolver.java then passes the attacker-controlled name to handlebars.compile(), allowing an unauthenticated remote attacker to read files accessible to the JVM when an application exposes a controller with a user-influenced view name. This issue is fixed in version 4.5.3.
Which versions are affected by CVE-2026-63490?
2 open source packages ship an affected version, including com.github.jknack:handlebars-springmvc.
| Package | Affected | Fixed in |
|---|---|---|
com.github.jknack:handlebars-springmvc Maven | All versions | 4.5.3 |
com.github.jknack:handlebars-springmvc Maven | All versions | 4.5.3 |
How do I fix CVE-2026-63490?
Upgrade com.github.jknack:handlebars-springmvc to 4.5.3 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-63490 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-63490 exists.
Sources
Also known as GHSA-g29j-rwfv-h99w.