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Merge pull request #9742 from smehta23/feat/SM/java_partial_path_traversal_vulnerability
[JAVA] Partial Path Traversal Vuln Query
2 parents 0adb588 + 1a3dc1d commit 774e379

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‎java/ql/lib/semmle/code/java/security/PartialPathTraversal.qll‎

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/** Provides classes to reason about partial path traversal vulnerabilities. */
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import java
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private import semmle.code.java.dataflow.DataFlow
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private import semmle.code.java.environment.SystemProperty
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private class MethodStringStartsWith extends Method {
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MethodStringStartsWith() {
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this.getDeclaringType() instanceof TypeString and
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this.hasName("startsWith")
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}
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}
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private class MethodFileGetCanonicalPath extends Method {
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MethodFileGetCanonicalPath() {
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this.getDeclaringType() instanceof TypeFile and
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this.hasName("getCanonicalPath")
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}
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}
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private class MethodAccessFileGetCanonicalPath extends MethodAccess {
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MethodAccessFileGetCanonicalPath() { this.getMethod() instanceof MethodFileGetCanonicalPath }
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}
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abstract private class FileSeparatorExpr extends Expr { }
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private class SystemPropFileSeparatorExpr extends FileSeparatorExpr {
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SystemPropFileSeparatorExpr() { this = getSystemProperty("file.separator") }
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}
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private class StringLiteralFileSeparatorExpr extends FileSeparatorExpr, StringLiteral {
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StringLiteralFileSeparatorExpr() {
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this.getValue().matches("%/") or this.getValue().matches("%\\")
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}
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}
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private class CharacterLiteralFileSeparatorExpr extends FileSeparatorExpr, CharacterLiteral {
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CharacterLiteralFileSeparatorExpr() { this.getValue() = "/" or this.getValue() = "\\" }
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}
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private class FileSeparatorAppend extends AddExpr {
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FileSeparatorAppend() { this.getRightOperand() instanceof FileSeparatorExpr }
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}
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private predicate isSafe(Expr expr) {
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DataFlow::localExprFlow(any(Expr e |
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e instanceof FileSeparatorAppend or e instanceof FileSeparatorExpr
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), expr)
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}
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/**
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* A method access that returns a boolean that incorrectly guards against Partial Path Traversal.
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*/
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class PartialPathTraversalMethodAccess extends MethodAccess {
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PartialPathTraversalMethodAccess() {
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this.getMethod() instanceof MethodStringStartsWith and
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DataFlow::localExprFlow(any(MethodAccessFileGetCanonicalPath gcpma), this.getQualifier()) and
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not isSafe(this.getArgument(0))
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}
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}

‎java/ql/lib/semmle/code/java/security/PartialPathTraversalQuery.qll‎

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/** Provides taint tracking configurations to be used in partial path traversal queries. */
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import java
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import semmle.code.java.security.PartialPathTraversal
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import semmle.code.java.dataflow.DataFlow
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import semmle.code.java.dataflow.ExternalFlow
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import semmle.code.java.dataflow.TaintTracking
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import semmle.code.java.dataflow.FlowSources
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/**
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* A taint-tracking configuration for unsafe user input
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* that is used to validate against path traversal, but is insufficient
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* and remains vulnerable to Partial Path Traversal.
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*/
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class PartialPathTraversalFromRemoteConfig extends TaintTracking::Configuration {
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PartialPathTraversalFromRemoteConfig() { this = "PartialPathTraversalFromRemoteConfig" }
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override predicate isSource(DataFlow::Node node) { node instanceof RemoteFlowSource }
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override predicate isSink(DataFlow::Node node) {
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any(PartialPathTraversalMethodAccess ma).getQualifier() = node.asExpr()
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}
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}

‎java/ql/src/Security/CWE/CWE-023/PartialPathTraversal.qhelp‎

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<!DOCTYPE qhelp PUBLIC
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"-//Semmle//qhelp//EN"
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"qhelp.dtd">
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<qhelp>
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<overview>
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<p>A common way to check that a user-supplied path <code>SUBDIR</code> falls inside a directory <code>DIR</code>
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is to use <code>getCanonicalPath()</code> to remove any path-traversal elements and then check that <code>DIR</code>
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is a prefix. However, if <code>DIR</code> is not slash-terminated, this can unexpectedly allow access to siblings of <code>DIR</code>.</p>
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<p>See also <code>java/partial-path-traversal-from-remote</code>, which is similar to this query but only flags instances with evidence of remote exploitability.</p>
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</overview>
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<include src="PartialPathTraversalRemainder.inc.qhelp"/>
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</qhelp>

‎java/ql/src/Security/CWE/CWE-023/PartialPathTraversal.ql‎

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/**
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* @name Partial path traversal vulnerability
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* @description A prefix used to check that a canonicalised path falls within another must be slash-terminated.
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* @kind problem
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* @problem.severity error
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* @security-severity 9.3
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* @precision medium
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* @id java/partial-path-traversal
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* @tags security
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* external/cwe/cwe-023
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*/
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import semmle.code.java.security.PartialPathTraversal
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from PartialPathTraversalMethodAccess ma
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select ma, "Partial Path Traversal Vulnerability due to insufficient guard against path traversal"

‎java/ql/src/Security/CWE/CWE-023/PartialPathTraversalBad.java‎

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public class PartialPathTraversalBad {
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public void example(File dir, File parent) throws IOException {
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if (!dir.getCanonicalPath().startsWith(parent.getCanonicalPath())) {
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throw new IOException("Invalid directory: " + dir.getCanonicalPath());
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}
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}
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}

‎java/ql/src/Security/CWE/CWE-023/PartialPathTraversalFromRemote.qhelp‎

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<!DOCTYPE qhelp PUBLIC
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"-//Semmle//qhelp//EN"
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"qhelp.dtd">
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<qhelp>
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<overview>
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<p>A common way to check that a user-supplied path <code>SUBDIR</code> falls inside a directory <code>DIR</code>
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is to use <code>getCanonicalPath()</code> to remove any path-traversal elements and then check that <code>DIR</code>
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is a prefix. However, if <code>DIR</code> is not slash-terminated, this can unexpectedly allow accessing siblings of <code>DIR</code>.</p>
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<p>See also <code>java/partial-path-traversal</code>, which is similar to this query,
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but may also flag non-remotely-exploitable instances of partial path traversal vulnerabilities.</p>
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</overview>
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<include src="PartialPathTraversalRemainder.inc.qhelp"/>
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</qhelp>

‎java/ql/src/Security/CWE/CWE-023/PartialPathTraversalFromRemote.ql‎

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/**
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* @name Partial path traversal vulnerability from remote
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* @description A prefix used to check that a canonicalised path falls within another must be slash-terminated.
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* @kind path-problem
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* @problem.severity error
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* @security-severity 9.3
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* @precision high
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* @id java/partial-path-traversal-from-remote
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* @tags security
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* external/cwe/cwe-023
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*/
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import semmle.code.java.security.PartialPathTraversalQuery
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import DataFlow::PathGraph
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from DataFlow::PathNode source, DataFlow::PathNode sink
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where any(PartialPathTraversalFromRemoteConfig config).hasFlowPath(source, sink)
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select sink.getNode(), source, sink,
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"Partial Path Traversal Vulnerability due to insufficient guard against path traversal from user-supplied data"

‎java/ql/src/Security/CWE/CWE-023/PartialPathTraversalGood.java‎

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public class PartialPathTraversalGood {
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public void example(File dir, File parent) throws IOException {
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if (!dir.getCanonicalPath().toPath().startsWith(parent.getCanonicalPath().toPath())) {
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throw new IOException("Invalid directory: " + dir.getCanonicalPath());
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}
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}
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}

‎java/ql/src/Security/CWE/CWE-023/PartialPathTraversalRemainder.inc.qhelp‎

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<!DOCTYPE qhelp PUBLIC
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"-//Semmle//qhelp//EN"
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"qhelp.dtd">
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<qhelp>
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<recommendation>
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<p>If the user should only access items within a certain directory <code>DIR</code>, ensure that <code>DIR</code> is slash-terminated
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before checking that <code>DIR</code> is a prefix of the user-provided path, <code>SUBDIR</code>. Note, Java's <code>getCanonicalPath()</code>
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returns a <b>non</b>-slash-terminated path string, so a slash must be added to <code>DIR</code> if that method is used.</p>
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</recommendation>
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<example>
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<p>
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In this example, the <code>if</code> statement checks if <code>parent.getCanonicalPath()</code>
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is a prefix of <code>dir.getCanonicalPath()</code>. However, <code>parent.getCanonicalPath()</code> is
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not slash-terminated. This means that users that supply <code>dir</code> may be also allowed to access siblings of <code>parent</code>
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and not just children of <code>parent</code>, which is a security issue.
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</p>
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<sample src="PartialPathTraversalBad.java" />
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<p>
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In this example, the <code>if</code> statement checks if <code>parent.getCanonicalPath() + File.separator </code>
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is a prefix of <code>dir.getCanonicalPath()</code>. Because <code>parent.getCanonicalPath().toPath()</code> is
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indeed slash-terminated, the user supplying <code>dir</code> can only access children of
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<code>parent</code>, as desired.
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</p>
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<sample src="PartialPathTraversalGood.java" />
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</example>
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<references>
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<li>OWASP:
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<a href="https://owasp.org/www-community/attacks/Path_Traversal">Partial Path Traversal</a>.</li>
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<li>CVE-2022-23457:
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<a href="https://github.com/ESAPI/esapi-java-legacy/blob/develop/documentation/GHSL-2022-008_The_OWASP_Enterprise_Security_API.md"> ESAPI Vulnerability Report</a>.</li>
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</references>
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</qhelp>

‎java/ql/src/change-notes/2022-07-01-partial-path-traversal.md‎

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---
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category: newQuery
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---
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* A new query `java/partial-path-traversal` finds partial path traversal vulnerabilities resulting from incorrectly using
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`String#startsWith` to compare canonical paths.

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