diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9b33c604..df6580ed 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,9 @@
 Latest
 ------
 
+## Fixes
+* [#343](https://github.com/cleverage/process-bundle/issues/343) The temporary files of `FileSplitterTask` (`file_splitter`), `CsvSplitterTask` (`csv_splitter`) and of the JSON buffer of `ProcessLauncherTask` (`json_buffering`) are created with a random name, exclusively (an existing path, symbolic links included, is never reused) and readable by their owner only, instead of a name derived from the time (`uniqid()`), opened in `w` mode with the permissions of the umask. Update documentation, add tests.
+
 v5.4.1
 -----
 
diff --git a/docs/reference/tasks/csv_splitter_task.md b/docs/reference/tasks/csv_splitter_task.md
index 328f0b47..a7a4e89c 100644
--- a/docs/reference/tasks/csv_splitter_task.md
+++ b/docs/reference/tasks/csv_splitter_task.md
@@ -20,8 +20,9 @@ Accepted inputs
 Possible outputs
 ----------------
 
-`string`: path of a temporary CSV file (created in the system temporary directory) containing the headers and the next
-`max_lines` data lines of the source file (the last file may contain fewer lines).
+`string`: path of a temporary CSV file (created in the system temporary directory, with a random name and readable by
+its owner only) containing the headers and the next `max_lines` data lines of the source file (the last file may
+contain fewer lines).
 
 Options
 -------
diff --git a/docs/reference/tasks/file_splitter_task.md b/docs/reference/tasks/file_splitter_task.md
index 18282cf4..eeadd791 100644
--- a/docs/reference/tasks/file_splitter_task.md
+++ b/docs/reference/tasks/file_splitter_task.md
@@ -20,8 +20,9 @@ file path as input. Any other input is ignored.
 Possible outputs
 ----------------
 
-`string`: path of a temporary file (created in the system temporary directory, with a `.tmp` extension) containing the
-next `max_lines` lines of the source file (the last file may contain fewer lines).
+`string`: path of a temporary file (created in the system temporary directory, with a random name, a `.tmp` extension
+and readable by its owner only) containing the next `max_lines` lines of the source file (the last file may contain
+fewer lines).
 
 Options
 -------
diff --git a/src/Filesystem/TemporaryFile.php b/src/Filesystem/TemporaryFile.php
new file mode 100644
index 00000000..323714fc
--- /dev/null
+++ b/src/Filesystem/TemporaryFile.php
@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the CleverAge/ProcessBundle package.
+ *
+ * Copyright (c) Clever-Age
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace CleverAge\ProcessBundle\Filesystem;
+
+use CleverAge\ProcessBundle\Exception\RuntimeException;
+
+/**
+ * Creates the temporary files of the bundle in the system temporary directory: random name, exclusive creation (an
+ * existing path, symbolic links included, is never reused) and readable by their owner only.
+ *
+ * @internal
+ */
+final class TemporaryFile
+{
+    /**
+     * Creates an empty file and returns its path.
+     */
+    public static function create(string $prefix, string $suffix = ''): string
+    {
+        $path = sys_get_temp_dir().\DIRECTORY_SEPARATOR.$prefix.bin2hex(random_bytes(16)).$suffix;
+        $file = @fopen($path, 'x');
+        if (false === $file) {
+            throw new RuntimeException("Unable to create temporary file {$path}");
+        }
+        fclose($file);
+        chmod($path, 0o600);
+
+        return $path;
+    }
+}
diff --git a/src/Model/SubprocessInstance.php b/src/Model/SubprocessInstance.php
index 274b9f4e..33ff59e9 100644
--- a/src/Model/SubprocessInstance.php
+++ b/src/Model/SubprocessInstance.php
@@ -14,6 +14,7 @@
 namespace CleverAge\ProcessBundle\Model;
 
 use CleverAge\ProcessBundle\Exception\RuntimeException;
+use CleverAge\ProcessBundle\Filesystem\TemporaryFile;
 use Symfony\Component\Filesystem\Filesystem;
 use Symfony\Component\HttpKernel\KernelInterface;
 use Symfony\Component\OptionsResolver\OptionsResolver;
@@ -29,7 +30,10 @@ class SubprocessInstance
 
     protected Process $process;
 
-    protected string $bufferPath;
+    /**
+     * JSON buffer, in the system temporary directory (the project directory may be read-only, e.g. in a container).
+     */
+    protected string $bufferPath = '';
 
     /**
      * @var array<string, mixed>
@@ -75,8 +79,6 @@ public function __construct(
             $consolePath = $consolePath->getProjectDir().'/bin/console';
         }
         $this->consolePath = $consolePath;
-        // The project directory may be read-only (e.g. in a container)
-        $this->bufferPath = sys_get_temp_dir().'/cdm_buffer_'.uniqid('', true).'.json-stream';
     }
 
     /**
@@ -104,6 +106,8 @@ public function buildProcess(): static
         }
 
         if ($this->options[self::OPTION_JSON_BUFFERING]) {
+            // Created before the sub-process writes into it: random name, exclusive creation, owner only
+            $this->bufferPath = TemporaryFile::create('cdm_buffer_', '.json-stream');
             $arguments = [...$arguments, '--output='.$this->bufferPath, '--output-format=json-stream'];
         }
 
diff --git a/src/Task/File/Csv/CsvSplitterTask.php b/src/Task/File/Csv/CsvSplitterTask.php
index 7d7a440e..d6c22cf5 100644
--- a/src/Task/File/Csv/CsvSplitterTask.php
+++ b/src/Task/File/Csv/CsvSplitterTask.php
@@ -16,6 +16,7 @@
 use CleverAge\ProcessBundle\Exception\RuntimeException;
 use CleverAge\ProcessBundle\Filesystem\CsvFile;
 use CleverAge\ProcessBundle\Filesystem\CsvResource;
+use CleverAge\ProcessBundle\Filesystem\TemporaryFile;
 use CleverAge\ProcessBundle\Model\ProcessState;
 use Symfony\Component\OptionsResolver\OptionsResolver;
 
@@ -93,7 +94,7 @@ public function finalize(ProcessState $state): void
 
     protected function splitCsv(CsvResource $csv, int $maxLines): string
     {
-        $tmpFilePath = sys_get_temp_dir().\DIRECTORY_SEPARATOR.'php_'.uniqid('process', false).'.csv';
+        $tmpFilePath = TemporaryFile::create('php_process', '.csv');
         $tmpFile = fopen($tmpFilePath, 'wb+');
         if (false === $tmpFile) {
             throw new RuntimeException("Unable to open temporary file {$tmpFilePath}");
diff --git a/src/Task/File/FileSplitterTask.php b/src/Task/File/FileSplitterTask.php
index f2a4fcb0..f0cb6c1c 100644
--- a/src/Task/File/FileSplitterTask.php
+++ b/src/Task/File/FileSplitterTask.php
@@ -14,6 +14,7 @@
 namespace CleverAge\ProcessBundle\Task\File;
 
 use CleverAge\ProcessBundle\Filesystem\SplFile;
+use CleverAge\ProcessBundle\Filesystem\TemporaryFile;
 use CleverAge\ProcessBundle\Model\AbstractConfigurableTask;
 use CleverAge\ProcessBundle\Model\IterableTaskInterface;
 use CleverAge\ProcessBundle\Model\ProcessState;
@@ -78,7 +79,7 @@ public function next(ProcessState $state): bool
 
     protected function splitFile(SplFile $file, int $maxLines): string
     {
-        $tmpFilePath = sys_get_temp_dir().\DIRECTORY_SEPARATOR.'php_'.uniqid('process', false).'.tmp';
+        $tmpFilePath = TemporaryFile::create('php_process', '.tmp');
         $splitFile = new SplFile($tmpFilePath, 'wb', []);
 
         $writtenLines = 0;
diff --git a/tests/Filesystem/TemporaryFileTest.php b/tests/Filesystem/TemporaryFileTest.php
new file mode 100644
index 00000000..acebb15b
--- /dev/null
+++ b/tests/Filesystem/TemporaryFileTest.php
@@ -0,0 +1,47 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the CleverAge/ProcessBundle package.
+ *
+ * Copyright (c) Clever-Age
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace CleverAge\ProcessBundle\Tests\Filesystem;
+
+use CleverAge\ProcessBundle\Filesystem\TemporaryFile;
+use PHPUnit\Framework\TestCase;
+
+#[\PHPUnit\Framework\Attributes\CoversClass(TemporaryFile::class)]
+class TemporaryFileTest extends TestCase
+{
+    public function testAnEmptyFileReadableByItsOwnerOnlyIsCreated(): void
+    {
+        $path = TemporaryFile::create('temporary_file_test_', '.csv');
+        try {
+            self::assertMatchesRegularExpression(
+                '#^'.preg_quote(sys_get_temp_dir(), '#').'/temporary_file_test_[0-9a-f]{32}\.csv$#',
+                $path
+            );
+            self::assertFileExists($path);
+            self::assertSame(0, filesize($path));
+            self::assertSame(0o600, fileperms($path) & 0o777);
+        } finally {
+            unlink($path);
+        }
+    }
+
+    public function testEachFileHasItsOwnName(): void
+    {
+        $first = TemporaryFile::create('temporary_file_test_');
+        $second = TemporaryFile::create('temporary_file_test_');
+        unlink($first);
+        unlink($second);
+
+        self::assertNotSame($first, $second);
+    }
+}
diff --git a/tests/Model/SubprocessInstanceTest.php b/tests/Model/SubprocessInstanceTest.php
index 6e0a482c..c2b76b73 100644
--- a/tests/Model/SubprocessInstanceTest.php
+++ b/tests/Model/SubprocessInstanceTest.php
@@ -13,12 +13,15 @@
 
 namespace CleverAge\ProcessBundle\Tests\Model;
 
+use CleverAge\ProcessBundle\Filesystem\TemporaryFile;
 use CleverAge\ProcessBundle\Model\SubprocessInstance;
 use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\UsesClass;
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\HttpKernel\KernelInterface;
 
 #[CoversClass(SubprocessInstance::class)]
+#[UsesClass(TemporaryFile::class)]
 class SubprocessInstanceTest extends TestCase
 {
     private string $projectDir;
@@ -61,9 +64,15 @@ public function testJsonBufferIsWrittenInTheTemporaryDirectory(): void
             ->buildProcess();
 
         $this->assertMatchesRegularExpression(
-            '#\'--output='.preg_quote(sys_get_temp_dir(), '#').'/cdm_buffer_[^/\']+\.json-stream\' \'--output-format=json-stream\'#',
+            '#\'--output=('.preg_quote(sys_get_temp_dir(), '#').'/cdm_buffer_[0-9a-f]{32}\.json-stream)\' \'--output-format=json-stream\'#',
             $subprocess->getProcess()->getCommandLine()
         );
+        preg_match('#--output=([^\']+)#', $subprocess->getProcess()->getCommandLine(), $matches);
+        $bufferPath = $matches[1] ?? '';
+        // Created before the sub-process writes into it, readable by its owner only
+        $this->assertFileExists($bufferPath);
+        $this->assertSame(0o600, fileperms($bufferPath) & 0o777);
+        unlink($bufferPath);
     }
 
     public function testMissingConsoleThrows(): void
diff --git a/tests/Task/File/Csv/CsvSplitterTaskTest.php b/tests/Task/File/Csv/CsvSplitterTaskTest.php
index 76aa2e94..14171178 100644
--- a/tests/Task/File/Csv/CsvSplitterTaskTest.php
+++ b/tests/Task/File/Csv/CsvSplitterTaskTest.php
@@ -18,6 +18,7 @@
 use CleverAge\ProcessBundle\Context\ContextualOptionResolver;
 use CleverAge\ProcessBundle\Filesystem\CsvFile;
 use CleverAge\ProcessBundle\Filesystem\CsvResource;
+use CleverAge\ProcessBundle\Filesystem\TemporaryFile;
 use CleverAge\ProcessBundle\Model\AbstractConfigurableTask;
 use CleverAge\ProcessBundle\Model\ProcessHistory;
 use CleverAge\ProcessBundle\Model\ProcessState;
@@ -33,6 +34,7 @@
 use Symfony\Component\OptionsResolver\Exception\InvalidOptionsException;
 
 #[\PHPUnit\Framework\Attributes\CoversClass(CsvSplitterTask::class)]
+#[\PHPUnit\Framework\Attributes\UsesClass(TemporaryFile::class)]
 #[\PHPUnit\Framework\Attributes\UsesClass(CsvReaderTask::class)]
 #[\PHPUnit\Framework\Attributes\UsesClass(InputCsvReaderTask::class)]
 #[\PHPUnit\Framework\Attributes\UsesClass(AbstractCsvTask::class)]
diff --git a/tests/Task/File/FileSplitterTaskTest.php b/tests/Task/File/FileSplitterTaskTest.php
index 8bc84f7f..8dbbba88 100644
--- a/tests/Task/File/FileSplitterTaskTest.php
+++ b/tests/Task/File/FileSplitterTaskTest.php
@@ -17,6 +17,7 @@
 use CleverAge\ProcessBundle\Configuration\TaskConfiguration;
 use CleverAge\ProcessBundle\Context\ContextualOptionResolver;
 use CleverAge\ProcessBundle\Filesystem\SplFile;
+use CleverAge\ProcessBundle\Filesystem\TemporaryFile;
 use CleverAge\ProcessBundle\Model\ProcessHistory;
 use CleverAge\ProcessBundle\Model\ProcessState;
 use CleverAge\ProcessBundle\Task\File\FileSplitterTask;
@@ -25,6 +26,7 @@
 use Symfony\Component\OptionsResolver\Exception\InvalidOptionsException;
 
 #[\PHPUnit\Framework\Attributes\CoversClass(FileSplitterTask::class)]
+#[\PHPUnit\Framework\Attributes\UsesClass(TemporaryFile::class)]
 #[\PHPUnit\Framework\Attributes\UsesClass(SplFile::class)]
 #[\PHPUnit\Framework\Attributes\UsesClass(ProcessConfiguration::class)]
 #[\PHPUnit\Framework\Attributes\UsesClass(TaskConfiguration::class)]