From b103aaa1f612b866d62643907153b1881fb1e871 Mon Sep 17 00:00:00 2001
From: Ian Kettle <25729118+icikle@users.noreply.github.com>
Date: Tue, 15 Sep 2026 09:03:31 +1200
Subject: [PATCH 1/2] Fix inflater cache race in NestedJarFileResources

Update `NestedJarFileResources` to fix a race condition that could
result in a `NullPointerException`.

The methods `getOrCreateInflater` and `endOrCacheInflater` both
synchronize on a local `inflaterCache` variable but attempted to use the
`this.inflaterCache` instance which could be set to null.

The `releaseInflators` method had a synchronized block for ending each
inflater but the cache was being nulled out outside the block meaning that
the other 2 methods mentioned could hit the race condition.

Signed-off-by: Ian Kettle <25729118+icikle@users.noreply.github.com>

See gh-51744
---
 .../boot/loader/jar/NestedJarFileResources.java    | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/NestedJarFileResources.java b/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/NestedJarFileResources.java
index 41fc29b55ce..812c7d191fb 100644
--- a/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/NestedJarFileResources.java
+++ b/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/NestedJarFileResources.java
@@ -116,7 +116,7 @@ class NestedJarFileResources implements Runnable {
 		Deque<Inflater> inflaterCache = this.inflaterCache;
 		if (inflaterCache != null) {
 			synchronized (inflaterCache) {
-				Inflater inflater = this.inflaterCache.poll();
+				Inflater inflater = inflaterCache.poll();
 				if (inflater != null) {
 					return inflater;
 				}
@@ -136,7 +136,7 @@ class NestedJarFileResources implements Runnable {
 			synchronized (inflaterCache) {
 				if (this.inflaterCache == inflaterCache && inflaterCache.size() < INFLATER_CACHE_LIMIT) {
 					inflater.reset();
-					this.inflaterCache.add(inflater);
+					inflaterCache.add(inflater);
 					return;
 				}
 			}
@@ -167,13 +167,13 @@ class NestedJarFileResources implements Runnable {
 	private IOException releaseInflators(IOException exceptionChain) {
 		Deque<Inflater> inflaterCache = this.inflaterCache;
 		if (inflaterCache != null) {
-			try {
-				synchronized (inflaterCache) {
+			synchronized (inflaterCache) {
+				try {
 					inflaterCache.forEach(Inflater::end);
 				}
-			}
-			finally {
-				this.inflaterCache = null;
+				finally {
+					this.inflaterCache = null;
+				}
 			}
 		}
 		return exceptionChain;

From d6aac54e2e2bbb00b7ee60a0ad551a8d2d2b0730 Mon Sep 17 00:00:00 2001
From: Phillip Webb <phil.webb@broadcom.com>
Date: Mon, 14 Sep 2026 17:34:36 -0700
Subject: [PATCH 2/2] Polish 'Fix inflater cache race in
 NestedJarFileResources'

See gh-51744
---
 .../springframework/boot/loader/jar/NestedJarFileResources.java  | 1 +
 1 file changed, 1 insertion(+)

diff --git a/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/NestedJarFileResources.java b/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/NestedJarFileResources.java
index 812c7d191fb..bf4aa5eded4 100644
--- a/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/NestedJarFileResources.java
+++ b/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/NestedJarFileResources.java
@@ -37,6 +37,7 @@ import org.springframework.boot.loader.zip.ZipContent.Kind;
  * for registration with a {@link Cleaner}.
  *
  * @author Phillip Webb
+ * @author Ian Kettle
  */
 class NestedJarFileResources implements Runnable {