CVE-2021-32769

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') in micronaut-core

router:
  static-resources:
    assets:
      enabled: true
      mapping: /.assets/public/**
      paths: file:/home/lstrmiska/test/

Micronaut can potentially leak sensitive information.

See https://cwe.mitre.org/data/definitions/22.html

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-2021-32769 has a CVSS score of 7.5 (High). 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 (2.5.9); upgrading removes the vulnerable code path.

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diff --git a/core/src/main/java/io/micronaut/core/io/file/DefaultFileSystemResourceLoader.java b/core/src/main/java/io/micronaut/core/io/file/DefaultFileSystemResourceLoader.java
index 2f5a91403..19d3b7f05 100644
--- a/core/src/main/java/io/micronaut/core/io/file/DefaultFileSystemResourceLoader.java
+++ b/core/src/main/java/io/micronaut/core/io/file/DefaultFileSystemResourceLoader.java
@@ -69,6 +69,9 @@ public class DefaultFileSystemResourceLoader implements FileSystemResourceLoader
     @Override
     public Optional<InputStream> getResourceAsStream(String path) {
         Path filePath = getFilePath(normalize(path));
+        if (pathOutsideBase(filePath)) {
+            return Optional.empty();
+        }
         try {
             return Optional.of(Files.newInputStream(filePath));
         } catch (IOException e) {
@@ -79,7 +82,7 @@ public class DefaultFileSystemResourceLoader implements FileSystemResourceLoader
     @Override
     public Optional<URL> getResource(String path) {
         Path filePath = getFilePath(normalize(path));
-        if (Files.exists(filePath) && Files.isReadable(filePath) && !Files.isDirectory(filePath)) {
+        if (!pathOutsideBase(filePath) && Files.exists(filePath) && Files.isReadable(filePath) && !Files.isDirectory(filePath)) {
             try {
                 URL url = filePath.toUri().toURL();
                 return Optional.of(url);
@@ -117,4 +120,15 @@ public class DefaultFileSystemResourceLoader implements FileSystemResourceLoader
     private Path getFilePath(String path) {
         return baseDirPath.map(dir -> dir.resolve(path)).orElseGet(() -> Paths.get(path));
     }
+
+    private boolean pathOutsideBase(Path path) {
+        if (baseDirPath.isPresent()) {
+            Path baseDir = baseDirPath.get();
+            if (path.isAbsolute() == baseDir.isAbsolute()) {
+                Path relativePath = baseDir.relativize(path);
+                return relativePath.startsWith("..");
+            }
+        }
+        return false;
+    }
 }
-- 

1. What is CVE-2021-32769? CVE-2021-32769 is a high-severity path traversal vulnerability in io.micronaut:micronaut-http-server-netty (maven), affecting versions < 2.5.9. It is fixed in 2.5.9. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
2. How severe is CVE-2021-32769? CVE-2021-32769 has a CVSS score of 7.5 (High). 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.
3. Which versions of io.micronaut:micronaut-http-server-netty are affected by CVE-2021-32769? io.micronaut:micronaut-http-server-netty (maven) versions < 2.5.9 is affected.
4. Is there a fix for CVE-2021-32769? Yes. CVE-2021-32769 is fixed in 2.5.9. Upgrade to this version or later.
5. Is CVE-2021-32769 exploitable, and should I be worried? Whether CVE-2021-32769 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
6. What actually determines whether CVE-2021-32769 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.
7. How do I fix CVE-2021-32769? Upgrade io.micronaut:micronaut-http-server-netty to 2.5.9 or later.

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