diff --git a/action-types.yml b/action-types.yml
index e567ea3..6dde1a6 100644
--- a/action-types.yml
+++ b/action-types.yml
@@ -26,3 +26,5 @@ inputs:
     type: string
   docker-network-alias:
     type: string
+  mongodb-extra-env:
+    type: string
diff --git a/action.yml b/action.yml
index bd0b05f..3e15d84 100644
--- a/action.yml
+++ b/action.yml
@@ -71,6 +71,11 @@ inputs:
     required: false
     default: ''
 
+  mongodb-extra-env:
+    description: 'Extra environment variables to pass to the MongoDB container, one KEY=VALUE per line (e.g. "GLIBC_TUNABLES=glibc.pthread.rseq=1")'
+    required: false
+    default: ''
+
 runs:
   using: 'docker'
   image: 'Dockerfile'
@@ -88,4 +93,5 @@ runs:
     - ${{ inputs.mongodb-replica-set-host }}
     - ${{ inputs.docker-network }}
     - ${{ inputs.docker-network-alias }}
+    - ${{ inputs.mongodb-extra-env }}
   post-entrypoint: /stop-mongodb.sh
diff --git a/start-mongodb.sh b/start-mongodb.sh
index b34b56b..025103e 100755
--- a/start-mongodb.sh
+++ b/start-mongodb.sh
@@ -14,6 +14,7 @@ MONGODB_AUTHSOURCE=${10}
 MONGODB_REPLICA_SET_HOST=${11:-"localhost"}
 DOCKER_NETWORK=${12}
 DOCKER_NETWORK_ALIAS=${13:-$MONGODB_CONTAINER_NAME}
+MONGODB_EXTRA_ENV=${14}
 
 # If DOCKER_NETWORK not provided, try to detect the default GitHub Actions network
 if [ -z "$DOCKER_NETWORK" ]; then
@@ -26,6 +27,17 @@ if [ -n "$DOCKER_NETWORK" ]; then
   NETWORK_ARGS="--network $DOCKER_NETWORK --network-alias $DOCKER_NETWORK_ALIAS"
 fi
 
+# Build extra -e flags from newline-separated KEY=VALUE pairs
+EXTRA_ENV_ARGS=""
+if [ -n "$MONGODB_EXTRA_ENV" ]; then
+  while IFS= read -r env_line; do
+    [ -z "$env_line" ] && continue
+    EXTRA_ENV_ARGS="$EXTRA_ENV_ARGS -e $env_line"
+  done <<EOF
+$MONGODB_EXTRA_ENV
+EOF
+fi
+
 # Echo selected network info for visibility
 echo "::group::Selecting Docker network"
 if [ -n "$DOCKER_NETWORK" ]; then
@@ -117,6 +129,7 @@ if [ -z "$MONGODB_REPLICA_SET" ]; then
     -e MONGO_INITDB_DATABASE=$MONGODB_DB \
     -e MONGO_INITDB_ROOT_USERNAME=$MONGODB_USERNAME \
     -e MONGO_INITDB_ROOT_PASSWORD=$MONGODB_PASSWORD \
+    $EXTRA_ENV_ARGS \
     --detach $MONGODB_IMAGE:$MONGODB_VERSION --port $MONGODB_PORT
 
   if [ $? -ne 0 ]; then
@@ -169,6 +182,7 @@ docker run --name $MONGODB_CONTAINER_NAME \
   -e MONGO_INITDB_ROOT_PASSWORD=$MONGODB_PASSWORD \
   -e MONGO_KEY=$MONGODB_KEY \
   -e MONGO_KEY_FILE=/tmp/mongo-keyfile \
+  $EXTRA_ENV_ARGS \
   --detach \
   --entrypoint bash \
   $MONGODB_IMAGE:$MONGODB_VERSION \
@@ -205,10 +219,21 @@ docker exec --tty $MONGODB_CONTAINER_NAME $MONGODB_CLIENT --port $MONGODB_PORT $
   })
 "
 
+if [ $? -ne 0 ]; then
+  echo "Error initiating replica set [$MONGODB_REPLICA_SET]"
+  exit 2
+fi
+
 echo "Success! Initiated replica set [$MONGODB_REPLICA_SET]"
 echo "::endgroup::"
 
 
 echo "::group::Checking replica set status [$MONGODB_REPLICA_SET]"
 docker exec --tty $MONGODB_CONTAINER_NAME $MONGODB_CLIENT --port $MONGODB_PORT $MONGODB_ARGS --eval "rs.status()"
+
+if [ $? -ne 0 ]; then
+  echo "Error checking replica set status [$MONGODB_REPLICA_SET]"
+  exit 2
+fi
+
 echo "::endgroup::"