# 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.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 20 Aug 2026
- **Updated:** 25 Aug 2026
- **Also known as:** GHSA-g29j-rwfv-h99w

## 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.

Weakness: CWE-552 (Files or Directories Accessible to External Parties), CWE-23 (Relative Path Traversal), CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-63490?

2 open source packages ship an affected version, including com.github.jknack:handlebars-springmvc.


| Package | Ecosystem | 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.

## Is CVE-2026-63490 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-63490 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-63490 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-63490 exists.

Affected packages and fixed versions:
- com.github.jknack:handlebars-springmvc (Maven): affected all versions; fixed in 4.5.3
- com.github.jknack:handlebars-springmvc (Maven): affected all versions; fixed in 4.5.3

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-63490/ (Markdown: https://insights.sbomify.com/CVE-2026-63490/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-63490
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-63490
- OSV: https://osv.dev/vulnerability/CVE-2026-63490

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-63490/
Summaries are generated and may contain mistakes; the official description above is the record.