diff --git a/external-dependencies/googletest/Dockerfile b/external-dependencies/googletest/Dockerfile
index cffb34465..447229882 100644
--- a/external-dependencies/googletest/Dockerfile
+++ b/external-dependencies/googletest/Dockerfile
@@ -55,23 +55,26 @@ RUN curl -fsSL http://${RME_ADMINSRV}/rme/deb_and_rpm_signage_key.pub --output /
 
 ARG GTEST_VERSION=1.15.2
 
+# Air-gapped Harbor registry URL
+ARG HARBOR_URL=https://internal-repo.sl.defence-elec.de
+
 # Install build dependencies
 RUN apt-get update && apt-get install -y --no-install-recommends \
-    build-essential cmake git \
+    build-essential cmake curl \
     && rm -rf /var/lib/apt/lists/*
 
-# Clone and build GoogleTest
-RUN git clone --depth 1 --branch v${GTEST_VERSION} \
-    https://github.com/google/googletest.git /tmp/googletest \
-    && cd /tmp/googletest \
-    && mkdir build && cd build \
-    && cmake -DCMAKE_BUILD_TYPE=Release \
-             -DCMAKE_INSTALL_PREFIX=/usr/local \
-             -DBUILD_SHARED_LIBS=ON \
-             .. \
-    && cmake --build . -j$(nproc) \
-    && cmake --install . \
-    && rm -rf /tmp/googletest
+# Download and build GoogleTest from air-gapped Harbor registry
+RUN curl -L -o /tmp/googletest-${GTEST_VERSION}.tar.gz ${HARBOR_URL}/googletest-${GTEST_VERSION}.tar.gz && \
+    tar -xzf /tmp/googletest-${GTEST_VERSION}.tar.gz -C /tmp && \
+    cd /tmp/googletest-${GTEST_VERSION} && \
+    mkdir build && cd build && \
+    cmake -DCMAKE_BUILD_TYPE=Release \
+          -DCMAKE_INSTALL_PREFIX=/usr/local \
+          -DBUILD_SHARED_LIBS=ON \
+          .. && \
+    cmake --build . -j$(nproc) && \
+    cmake --install . && \
+    rm -rf /tmp/googletest-${GTEST_VERSION}.tar.gz /tmp/googletest-${GTEST_VERSION}
 
 # Update library cache
 RUN ldconfig
diff --git a/external-dependencies/grantlee/Dockerfile b/external-dependencies/grantlee/Dockerfile
index 15cfca6d9..2d0daa780 100644
--- a/external-dependencies/grantlee/Dockerfile
+++ b/external-dependencies/grantlee/Dockerfile
@@ -56,26 +56,29 @@ RUN curl -fsSL http://${RME_ADMINSRV}/rme/deb_and_rpm_signage_key.pub --output /
 ARG QT_VERSION=6.10.2
 ARG GRANTLEE_VERSION=5.3.1
 
+# Air-gapped Harbor registry URL
+ARG HARBOR_URL=https://internal-repo.sl.defence-elec.de
+
 # Install build dependencies
 RUN apt-get update && apt-get install -y --no-install-recommends \
-    build-essential cmake git \
+    build-essential cmake curl \
     libqt6core6 libqt6gui6 libqt6widgets6 \
     qt6-base-dev \
     && rm -rf /var/lib/apt/lists/*
 
-# Clone and build Grantlee
-RUN git clone --depth 1 --branch ${GRANTLEE_VERSION} \
-    https://github.com/steveire/grantlee.git /tmp/grantlee \
-    && cd /tmp/grantlee \
-    && mkdir build && cd build \
-    && cmake -DCMAKE_BUILD_TYPE=Release \
-             -DCMAKE_INSTALL_PREFIX=/usr/local \
-             -DCMAKE_PREFIX_PATH=/opt/Qt/${QT_VERSION}/gcc_64 \
-             -DGRANTLEE_BUILD_WITH_QT6=ON \
-             .. \
-    && cmake --build . -j$(nproc) \
-    && cmake --install . \
-    && rm -rf /tmp/grantlee
+# Download and build Grantlee from air-gapped Harbor registry
+RUN curl -L -o /tmp/grantlee-${GRANTLEE_VERSION}.tar.gz ${HARBOR_URL}/grantlee-${GRANTLEE_VERSION}.tar.gz && \
+    tar -xzf /tmp/grantlee-${GRANTLEE_VERSION}.tar.gz -C /tmp && \
+    cd /tmp/grantlee-${GRANTLEE_VERSION} && \
+    mkdir build && cd build && \
+    cmake -DCMAKE_BUILD_TYPE=Release \
+          -DCMAKE_INSTALL_PREFIX=/usr/local \
+          -DCMAKE_PREFIX_PATH=/opt/Qt/${QT_VERSION}/gcc_64 \
+          -DGRANTLEE_BUILD_WITH_QT6=ON \
+          .. && \
+    cmake --build . -j$(nproc) && \
+    cmake --install . && \
+    rm -rf /tmp/grantlee-${GRANTLEE_VERSION}.tar.gz /tmp/grantlee-${GRANTLEE_VERSION}
 
 # Update library cache
 RUN ldconfig
diff --git a/external-dependencies/kdreports/Dockerfile b/external-dependencies/kdreports/Dockerfile
index 616b33ab0..6caa84f86 100644
--- a/external-dependencies/kdreports/Dockerfile
+++ b/external-dependencies/kdreports/Dockerfile
@@ -56,25 +56,28 @@ RUN curl -fsSL http://${RME_ADMINSRV}/rme/deb_and_rpm_signage_key.asc --output /
 ARG QT_VERSION=6.10.2
 ARG KDREPORTS_VERSION=2.3.0
 
+# Air-gapped Harbor registry URL
+ARG HARBOR_URL=https://internal-repo.sl.defence-elec.de
+
 # Install build dependencies
 RUN apt-get update && apt-get install -y --no-install-recommends \
-    build-essential cmake git \
+    build-essential cmake curl \
     libqt6core6 libqt6gui6 libqt6widgets6 libqt6xml6 \
     qt6-base-dev \
     && rm -rf /var/lib/apt/lists/*
 
-# Clone and build KDReports
-RUN git clone --depth 1 --branch kdreports-${KDREPORTS_VERSION} \
-    https://github.com/KDAB/KDReports.git /tmp/KDReports \
-    && cd /tmp/KDReports \
-    && mkdir build && cd build \
-    && cmake -DCMAKE_BUILD_TYPE=Release \
-             -DCMAKE_INSTALL_PREFIX=/usr/local \
-             -DCMAKE_PREFIX_PATH=/opt/Qt/${QT_VERSION}/gcc_64 \
-             -DKDReports_QT6=ON .. \
-    && cmake --build . -j$(nproc) \
-    && cmake --install . \
-    && rm -rf /tmp/KDReports
+# Download and build KDReports from air-gapped Harbor registry
+RUN curl -L -o /tmp/KDReports-2.3.0.tar.gz ${HARBOR_URL}/KDReports-2.3.0.tar.gz && \
+    tar -xzf /tmp/KDReports-2.3.0.tar.gz -C /tmp && \
+    cd /tmp/KDReports && \
+    mkdir build && cd build && \
+    cmake -DCMAKE_BUILD_TYPE=Release \
+          -DCMAKE_INSTALL_PREFIX=/usr/local \
+          -DCMAKE_PREFIX_PATH=/opt/Qt/${QT_VERSION}/gcc_64 \
+          -DKDReports_QT6=ON .. && \
+    cmake --build . -j$(nproc) && \
+    cmake --install . && \
+    rm -rf /tmp/KDReports-2.3.0.tar.gz /tmp/KDReports
 
 # Create header alias for legacy includes
 RUN ln -sfn /usr/local/include/KDReports-qt6 /usr/local/include/KDReports
diff --git a/external-dependencies/log4qt/Dockerfile b/external-dependencies/log4qt/Dockerfile
index c8f4da115..8392157e6 100644
--- a/external-dependencies/log4qt/Dockerfile
+++ b/external-dependencies/log4qt/Dockerfile
@@ -56,25 +56,28 @@ RUN curl -fsSL http://${RME_ADMINSRV}/rme/deb_and_rpm_signage_key.pub --output /
 ARG QT_VERSION=6.10.2
 ARG LOG4QT_VERSION=2.0.0
 
+# Air-gapped Harbor registry URL
+ARG HARBOR_URL=https://internal-repo.sl.defence-elec.de
+
 # Install build dependencies
 RUN apt-get update && apt-get install -y --no-install-recommends \
-    build-essential cmake git \
+    build-essential cmake curl \
     libqt6core6 libqt6gui6 libqt6widgets6 \
     qt6-base-dev \
     && rm -rf /var/lib/apt/lists/*
 
-# Clone and build Log4Qt
-RUN git clone --depth 1 --branch v${LOG4QT_VERSION} \
-    https://github.com/MeanEYE/Log4Qt.git /tmp/Log4Qt \
-    && cd /tmp/Log4Qt \
-    && mkdir build && cd build \
-    && cmake -DCMAKE_BUILD_TYPE=Release \
-             -DCMAKE_INSTALL_PREFIX=/usr/local \
-             -DCMAKE_PREFIX_PATH=/opt/Qt/${QT_VERSION}/gcc_64 \
-             .. \
-    && cmake --build . -j$(nproc) \
-    && cmake --install . \
-    && rm -rf /tmp/Log4Qt
+# Download and build Log4Qt from air-gapped Harbor registry
+RUN curl -L -o /tmp/Log4Qt-2.0.0.tar.gz ${HARBOR_URL}/Log4Qt-2.0.0.tar.gz && \
+    tar -xzf /tmp/Log4Qt-2.0.0.tar.gz -C /tmp && \
+    cd /tmp/Log4Qt && \
+    mkdir build && cd build && \
+    cmake -DCMAKE_BUILD_TYPE=Release \
+          -DCMAKE_INSTALL_PREFIX=/usr/local \
+          -DCMAKE_PREFIX_PATH=/opt/Qt/${QT_VERSION}/gcc_64 \
+          .. && \
+    cmake --build . -j$(nproc) && \
+    cmake --install . && \
+    rm -rf /tmp/Log4Qt-2.0.0.tar.gz /tmp/Log4Qt
 
 # Update library cache
 RUN ldconfig