diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d63fa97b..7082baf5 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -13,7 +13,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Install specific version 2.3 of OpenJPEG library
         run: wget https://github.com/uclouvain/openjpeg/releases/download/v2.3.0/openjpeg-v2.3.0-linux-x86_64.tar.gz -O /tmp/openjpeg.tar.gz && cd /tmp/ && tar -xvf /tmp/openjpeg.tar.gz
       - name: Set environment variable for OpenJPEG library
@@ -21,13 +21,13 @@ jobs:
       - name: Install TurboJPEG library
         run: sudo apt update && sudo apt install libturbojpeg
       - name: Set up JDK
-        uses: actions/setup-java@v3
+        uses: actions/setup-java@v4
         with:
           check-latest: true
           distribution: temurin
           java-version: ${{ matrix.java }}
       - name: Set up cache
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         env:
           cache-name: cache-maven-artifacts
         with:
@@ -46,9 +46,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Set up cache
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         env:
           cache-name: cache-maven-artifacts
         with:
@@ -65,7 +65,7 @@ jobs:
       # Publish snapshot
       - name: Set up JDK 11 for publishing a snapshot
         if: github.event_name == 'push' && endswith(env.PROJECT_VERSION, 'SNAPSHOT')
-        uses: actions/setup-java@v3
+        uses: actions/setup-java@v4
         with:
           check-latest: true
           distribution: temurin
@@ -82,7 +82,7 @@ jobs:
       # Publish release
       - name: Set up JDK 11 for publishing a release
         if: github.event_name == 'release' && !endswith(env.PROJECT_VERSION, 'SNAPSHOT')
-        uses: actions/setup-java@v3
+        uses: actions/setup-java@v4
         with:
           check-latest: true
           distribution: temurin
diff --git a/pom.xml b/pom.xml
index 526b0f3d..3df3f8a4 100644
--- a/pom.xml
+++ b/pom.xml
@@ -6,7 +6,7 @@
   <parent>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-parent</artifactId>
-    <version>2.7.18</version>
+    <version>3.4.0</version>
   </parent>
 
   <name>DigitalCollections: Hymir IIIF Server</name>
@@ -77,7 +77,7 @@
     <versionName>${project.version} manually built by ${user.name} at ${maven.build.timestamp}</versionName>
 
     <!-- versions are referenced in application-webjars.yml -->
-    <version.webjar-bootstrap>4.6.0</version.webjar-bootstrap>
+    <version.webjar-bootstrap>5.3.3</version.webjar-bootstrap>
     <version.webjar-html5shiv>3.7.3-1</version.webjar-html5shiv>
     <version.webjar-ie10-viewport-bug-workaround>1.0.3</version.webjar-ie10-viewport-bug-workaround>
     <version.webjar-jquery>3.7.1</version.webjar-jquery>
@@ -202,7 +202,7 @@
     <dependency>
       <groupId>net.logstash.logback</groupId>
       <artifactId>logstash-logback-encoder</artifactId>
-      <version>7.4</version>
+      <version>8.0</version>
       <scope>runtime</scope>
     </dependency>
     <dependency>