diff --git a/Build/gitlab-ci/nightly/functional.yml b/Build/gitlab-ci/nightly/functional.yml
index 04a86927ae6a..567dd6c340a5 100644
--- a/Build/gitlab-ci/nightly/functional.yml
+++ b/Build/gitlab-ci/nightly/functional.yml
@@ -1,4 +1,4 @@
-functional mariadb 10.10 php 8.3 max:
+functional mariadb 10.10 php 8.4 max:
   stage: functional
   tags:
     - metal2
@@ -7,8 +7,8 @@ functional mariadb 10.10 php 8.3 max:
     - schedules
   parallel: 6
   script:
-    - Build/Scripts/runTests.sh -s composerInstallMax -p 8.3
-    - Build/Scripts/runTests.sh -s functional -d mariadb -i 10.10 -p 8.3 -c $CI_NODE_INDEX/$CI_NODE_TOTAL
+    - Build/Scripts/runTests.sh -s composerInstallMax -p 8.4
+    - Build/Scripts/runTests.sh -s functional -d mariadb -i 10.10 -p 8.4 -c $CI_NODE_INDEX/$CI_NODE_TOTAL
 functional mariadb 10.4 php 8.2 min:
   stage: functional
   tags:
diff --git a/Build/gitlab-ci/pre-merge/functional.yml b/Build/gitlab-ci/pre-merge/functional.yml
index 1ffe3f9c7c91..25508810bd20 100644
--- a/Build/gitlab-ci/pre-merge/functional.yml
+++ b/Build/gitlab-ci/pre-merge/functional.yml
@@ -11,7 +11,7 @@ functional mariadb 10.4 php 8.3 pre-merge:
     - Build/Scripts/runTests.sh -s composerInstall -p 8.3
     - Build/Scripts/runTests.sh -s functional -d mariadb -i 10.4 -p 8.3 -c $CI_NODE_INDEX/$CI_NODE_TOTAL
 
-functional postgres 10 php 8.2 pre-merge:
+functional postgres 10 php 8.4 pre-merge:
   stage: main
   tags:
     - metal2
@@ -21,8 +21,8 @@ functional postgres 10 php 8.2 pre-merge:
       - main
   parallel: 10
   script:
-    - Build/Scripts/runTests.sh -s composerInstall -p 8.2
-    - Build/Scripts/runTests.sh -s functional -d postgres -i 10 -p 8.2 -c $CI_NODE_INDEX/$CI_NODE_TOTAL
+    - Build/Scripts/runTests.sh -s composerInstall -p 8.4
+    - Build/Scripts/runTests.sh -s functional -d postgres -i 10 -p 8.4 -c $CI_NODE_INDEX/$CI_NODE_TOTAL
 
 functional sqlite php 8.2 pre-merge:
   stage: main
diff --git a/Build/patches/darylldoyle-svg-sanitizer-php-8.4.diff b/Build/patches/darylldoyle-svg-sanitizer-php-8.4.diff
new file mode 100644
index 000000000000..a4c0cef6770c
--- /dev/null
+++ b/Build/patches/darylldoyle-svg-sanitizer-php-8.4.diff
@@ -0,0 +1,13 @@
+diff --git a/src/Exceptions/NestingException.php b/src/Exceptions/NestingException.php
+index 474b987..7acc842 100644
+--- a/src/Exceptions/NestingException.php
++++ b/src/Exceptions/NestingException.php
+@@ -18,7 +18,7 @@ class NestingException extends \Exception
+      * @param Exception|null   $previous
+      * @param \DOMElement|null $element
+      */
+-    public function __construct($message = "", $code = 0, Exception $previous = null, \DOMElement $element = null)
++    public function __construct($message = "", $code = 0, ?Exception $previous = null, ?\DOMElement $element = null)
+     {
+         $this->element = $element;
+         parent::__construct($message, $code, $previous);
diff --git a/Build/patches/patches.json b/Build/patches/patches.json
index 0b9a3d85d706..0fb273ef95f1 100644
--- a/Build/patches/patches.json
+++ b/Build/patches/patches.json
@@ -2,6 +2,9 @@
     "patches": {
         "firebase/php-jwt": {
             "firebase/php-jwt PHP 8.4": "Build/patches/firebase-php-jwt-572-php-8.4.diff"
+        },
+        "enshrined/svg-sanitize": {
+            "darylldoyle/svg-sanitize PHP 8.4": "Build/patches/darylldoyle-svg-sanitizer-php-8.4.diff"
         }
     }
 }
diff --git a/typo3/sysext/core/Tests/Functional/Resource/Fixtures/DirtySVG/external.svg b/typo3/sysext/core/Tests/Functional/Resource/Fixtures/DirtySVG/external.svg
index cd190cb20038..e6b36669565e 100644
--- a/typo3/sysext/core/Tests/Functional/Resource/Fixtures/DirtySVG/external.svg
+++ b/typo3/sysext/core/Tests/Functional/Resource/Fixtures/DirtySVG/external.svg
@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
 <svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" xml:space="preserve">
 <rect fill="url('http://example.com/benis.svg')" x="0" y="0" width="1000" height="1000"></rect>
diff --git a/typo3/sysext/core/Tests/Functional/Resource/Fixtures/DirtySVG/svgOne.svg b/typo3/sysext/core/Tests/Functional/Resource/Fixtures/DirtySVG/svgOne.svg
index f543a84b5f32..0799159aac6b 100644
--- a/typo3/sysext/core/Tests/Functional/Resource/Fixtures/DirtySVG/svgOne.svg
+++ b/typo3/sysext/core/Tests/Functional/Resource/Fixtures/DirtySVG/svgOne.svg
@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="UTF-8"?>
 <!-- Generator: Adobe Illustrator 16.0.0, SVG Export Plug-In . SVG Version: 6.00 Build 0)  -->
 <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
 <svg version="1.1" id="Layer_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
diff --git a/typo3/sysext/core/Tests/Functional/Resource/Fixtures/DirtySVG/xlinkLoop.svg b/typo3/sysext/core/Tests/Functional/Resource/Fixtures/DirtySVG/xlinkLoop.svg
index e8de02d74a56..28a0da673458 100644
--- a/typo3/sysext/core/Tests/Functional/Resource/Fixtures/DirtySVG/xlinkLoop.svg
+++ b/typo3/sysext/core/Tests/Functional/Resource/Fixtures/DirtySVG/xlinkLoop.svg
@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="UTF-8"?>
 <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 500 500">
   <!-- ping:pong section to be removed -->
   <g id="ping">
diff --git a/typo3/sysext/core/Tests/Functional/Resource/Security/SvgSanitizerTest.php b/typo3/sysext/core/Tests/Functional/Resource/Security/SvgSanitizerTest.php
index 00c04a68be56..a66640e09a02 100644
--- a/typo3/sysext/core/Tests/Functional/Resource/Security/SvgSanitizerTest.php
+++ b/typo3/sysext/core/Tests/Functional/Resource/Security/SvgSanitizerTest.php
@@ -54,9 +54,9 @@ public static function svgContentIsSanitizedDataProvider(): array
     public function svgContentIsSanitized(string $filePath, string $sanitizedFilePath): void
     {
         $sanitizer = new SvgSanitizer();
-        self::assertStringEqualsFile(
-            $sanitizedFilePath,
-            $sanitizer->sanitizeContent(file_get_contents($filePath))
-        );
+        $sanitizedFileContent = file_get_contents($sanitizedFilePath);
+        // Align lowercase / uppercase "UTF-8" in files - Casing changed in PHP 8.4 generated XML.
+        $sanitizedFileContent = str_replace('utf-8', 'UTF-8', $sanitizedFileContent);
+        self::assertEquals($sanitizedFileContent, $sanitizer->sanitizeContent(file_get_contents($filePath)));
     }
 }