diff --git a/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/JarURLConnection.java b/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/JarURLConnection.java
index 52b5e1487c..2130ba1395 100644
--- a/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/JarURLConnection.java
+++ b/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/JarURLConnection.java
@@ -255,6 +255,10 @@ final class JarURLConnection extends java.net.JarURLConnection {
 	static JarURLConnection get(URL url, JarFile jarFile) throws IOException {
 		StringSequence spec = new StringSequence(url.getFile());
 		int index = indexOfRootSpec(spec, jarFile.getPathFromRoot());
+		if (index == -1) {
+			return (Boolean.TRUE.equals(useFastExceptions.get()) ? NOT_FOUND_CONNECTION
+					: new JarURLConnection(url, null, EMPTY_JAR_ENTRY_NAME));
+		}
 		int separator;
 		while ((separator = spec.indexOf(SEPARATOR, index)) > 0) {
 			JarEntryName entryName = JarEntryName.get(spec.subSequence(index, separator));
@@ -275,7 +279,7 @@ final class JarURLConnection extends java.net.JarURLConnection {
 
 	private static int indexOfRootSpec(StringSequence file, String pathFromRoot) {
 		int separatorIndex = file.indexOf(SEPARATOR);
-		if (separatorIndex < 0) {
+		if (separatorIndex < 0 || !file.startsWith(pathFromRoot, separatorIndex)) {
 			return -1;
 		}
 		return separatorIndex + SEPARATOR.length() + pathFromRoot.length();
diff --git a/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/StringSequence.java b/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/StringSequence.java
index a1989f6083..c298cf6886 100644
--- a/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/StringSequence.java
+++ b/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/StringSequence.java
@@ -95,6 +95,17 @@ final class StringSequence implements CharSequence {
 		return this.source.indexOf(str, this.start + fromIndex) - this.start;
 	}
 
+	public boolean startsWith(CharSequence prefix) {
+		return startsWith(prefix, 0);
+	}
+
+	public boolean startsWith(CharSequence prefix, int toffset) {
+		if (length() - prefix.length() - toffset < 0) {
+			return false;
+		}
+		return subSequence(toffset, toffset + prefix.length()).equals(prefix);
+	}
+
 	@Override
 	public String toString() {
 		return this.source.substring(this.start, this.end);
@@ -117,10 +128,10 @@ final class StringSequence implements CharSequence {
 		if (this == obj) {
 			return true;
 		}
-		if (obj == null || getClass() != obj.getClass()) {
+		if (obj == null || !CharSequence.class.isInstance(obj)) {
 			return false;
 		}
-		StringSequence other = (StringSequence) obj;
+		CharSequence other = (CharSequence) obj;
 		int n = length();
 		if (n == other.length()) {
 			int i = 0;
diff --git a/spring-boot-project/spring-boot-tools/spring-boot-loader/src/test/java/org/springframework/boot/loader/jar/JarURLConnectionTests.java b/spring-boot-project/spring-boot-tools/spring-boot-loader/src/test/java/org/springframework/boot/loader/jar/JarURLConnectionTests.java
index 58f655f547..38ae048837 100644
--- a/spring-boot-project/spring-boot-tools/spring-boot-loader/src/test/java/org/springframework/boot/loader/jar/JarURLConnectionTests.java
+++ b/spring-boot-project/spring-boot-tools/spring-boot-loader/src/test/java/org/springframework/boot/loader/jar/JarURLConnectionTests.java
@@ -18,6 +18,7 @@ package org.springframework.boot.loader.jar;
 
 import java.io.ByteArrayInputStream;
 import java.io.File;
+import java.io.FileNotFoundException;
 import java.net.URL;
 
 import org.junit.Before;
@@ -149,6 +150,16 @@ public class JarURLConnectionTests {
 				.hasSameContentAs(new ByteArrayInputStream(new byte[] { 3 }));
 	}
 
+	@Test
+	public void connectionToEntryUsingWrongAbsoluteUrlForEntryFromNestedJarFile()
+			throws Exception {
+		URL url = new URL("jar:file:" + getAbsolutePath() + "!/w.jar!/3.dat");
+		JarFile nested = this.jarFile
+				.getNestedJarFile(this.jarFile.getEntry("nested.jar"));
+		this.thrown.expect(FileNotFoundException.class);
+		JarURLConnection.get(url, nested).getInputStream();
+	}
+
 	@Test
 	public void getContentLengthReturnsLengthOfUnderlyingEntry() throws Exception {
 		URL url = new URL(new URL("jar", null, -1,
diff --git a/spring-boot-project/spring-boot-tools/spring-boot-loader/src/test/java/org/springframework/boot/loader/jar/StringSequenceTests.java b/spring-boot-project/spring-boot-tools/spring-boot-loader/src/test/java/org/springframework/boot/loader/jar/StringSequenceTests.java
index 5d43e94f6e..d9d2d48ece 100644
--- a/spring-boot-project/spring-boot-tools/spring-boot-loader/src/test/java/org/springframework/boot/loader/jar/StringSequenceTests.java
+++ b/spring-boot-project/spring-boot-tools/spring-boot-loader/src/test/java/org/springframework/boot/loader/jar/StringSequenceTests.java
@@ -167,4 +167,46 @@ public class StringSequenceTests {
 		assertThat(a).isEqualTo(b).isNotEqualTo(c);
 	}
 
+	@Test
+	public void startsWithWhenExactMatch() {
+		assertThat(new StringSequence("abc").startsWith("abc")).isTrue();
+	}
+
+	@Test
+	public void startsWithWhenLongerAndStartsWith() {
+		assertThat(new StringSequence("abcd").startsWith("abc")).isTrue();
+	}
+
+	@Test
+	public void startsWithWhenLongerAndDoesNotStartWith() {
+		assertThat(new StringSequence("abcd").startsWith("abx")).isFalse();
+	}
+
+	@Test
+	public void startsWithWhenShorterAndDoesNotStartWith() {
+		assertThat(new StringSequence("ab").startsWith("abc")).isFalse();
+		assertThat(new StringSequence("ab").startsWith("c")).isFalse();
+	}
+
+	@Test
+	public void startsWithOffsetWhenExactMatch() {
+		assertThat(new StringSequence("xabc").startsWith("abc", 1)).isTrue();
+	}
+
+	@Test
+	public void startsWithOffsetWhenLongerAndStartsWith() {
+		assertThat(new StringSequence("xabcd").startsWith("abc", 1)).isTrue();
+	}
+
+	@Test
+	public void startsWithOffsetWhenLongerAndDoesNotStartWith() {
+		assertThat(new StringSequence("xabcd").startsWith("abx", 1)).isFalse();
+	}
+
+	@Test
+	public void startsWithOffsetWhenShorterAndDoesNotStartWith() {
+		assertThat(new StringSequence("xab").startsWith("abc", 1)).isFalse();
+		assertThat(new StringSequence("xab").startsWith("c", 1)).isFalse();
+	}
+
 }