diff --git a/apply.c b/apply.c
index 2b7cd930ef..850604c191 100644
--- a/apply.c
+++ b/apply.c
@@ -386,9 +386,19 @@ static void say_patch_name(FILE *output, const char *fmt, struct patch *patch)
 
 #define SLOP (16)
 
+/*
+ * apply.c isn't equipped to handle arbitrarily large patches, because
+ * it intermingles `unsigned long` with `int` for the type used to store
+ * buffer lengths.
+ *
+ * Only process patches that are just shy of 1 GiB large in order to
+ * avoid any truncation or overflow issues.
+ */
+#define MAX_APPLY_SIZE (1024UL * 1024 * 1023)
+
 static int read_patch_file(struct strbuf *sb, int fd)
 {
-	if (strbuf_read(sb, fd, 0) < 0)
+	if (strbuf_read(sb, fd, 0) < 0 || sb->len >= MAX_APPLY_SIZE)
 		return error_errno("git apply: failed to read");
 
 	/*
diff --git a/t/t4141-apply-too-large.sh b/t/t4141-apply-too-large.sh
new file mode 100755
index 0000000000..58742d4fc5
--- /dev/null
+++ b/t/t4141-apply-too-large.sh
@@ -0,0 +1,23 @@
+#!/bin/sh
+
+test_description='git apply with too-large patch'
+
+TEST_PASSES_SANITIZE_LEAK=true
+. ./test-lib.sh
+
+test_expect_success EXPENSIVE 'git apply rejects patches that are too large' '
+	sz=$((1024 * 1024 * 1023)) &&
+	{
+		cat <<-\EOF &&
+		diff --git a/file b/file
+		new file mode 100644
+		--- /dev/null
+		+++ b/file
+		@@ -0,0 +1 @@
+		EOF
+		test-tool genzeros
+	} | test_copy_bytes $sz | test_must_fail git apply 2>err &&
+	grep "git apply: failed to read" err
+'
+
+test_done