diff --git a/src/config/defaults.rs b/src/config/defaults.rs
index 09d146a..f02403e 100644
--- a/src/config/defaults.rs
+++ b/src/config/defaults.rs
@@ -185,6 +185,10 @@ pub(crate) fn default_proxy_protocol_header_timeout_ms() -> u64 {
     500
 }
 
+pub(crate) fn default_proxy_protocol_trusted_cidrs() -> Vec<IpNetwork> {
+    vec!["0.0.0.0/0".parse().unwrap(), "::/0".parse().unwrap()]
+}
+
 pub(crate) fn default_server_max_connections() -> u32 {
     10_000
 }
diff --git a/src/config/load.rs b/src/config/load.rs
index 8f12757..2a501ea 100644
--- a/src/config/load.rs
+++ b/src/config/load.rs
@@ -1263,6 +1263,10 @@ mod tests {
         assert_eq!(cfg.general.update_every, default_update_every());
         assert_eq!(cfg.server.listen_addr_ipv4, default_listen_addr_ipv4());
         assert_eq!(cfg.server.listen_addr_ipv6, default_listen_addr_ipv6_opt());
+        assert_eq!(
+            cfg.server.proxy_protocol_trusted_cidrs,
+            default_proxy_protocol_trusted_cidrs()
+        );
         assert_eq!(cfg.server.api.listen, default_api_listen());
         assert_eq!(cfg.server.api.whitelist, default_api_whitelist());
         assert_eq!(
@@ -1395,6 +1399,10 @@ mod tests {
 
         let server = ServerConfig::default();
         assert_eq!(server.listen_addr_ipv6, Some(default_listen_addr_ipv6()));
+        assert_eq!(
+            server.proxy_protocol_trusted_cidrs,
+            default_proxy_protocol_trusted_cidrs()
+        );
         assert_eq!(server.api.listen, default_api_listen());
         assert_eq!(server.api.whitelist, default_api_whitelist());
         assert_eq!(
@@ -1430,6 +1438,41 @@ mod tests {
         assert_eq!(access.users, default_access_users());
     }
 
+    #[test]
+    fn proxy_protocol_trusted_cidrs_missing_uses_trust_all_but_explicit_empty_stays_empty() {
+        let cfg_missing: ProxyConfig = toml::from_str(
+            r#"
+            [server]
+            [general]
+            [network]
+            [access]
+            "#,
+        )
+        .unwrap();
+        assert_eq!(
+            cfg_missing.server.proxy_protocol_trusted_cidrs,
+            default_proxy_protocol_trusted_cidrs()
+        );
+
+        let cfg_explicit_empty: ProxyConfig = toml::from_str(
+            r#"
+            [server]
+            proxy_protocol_trusted_cidrs = []
+
+            [general]
+            [network]
+            [access]
+            "#,
+        )
+        .unwrap();
+        assert!(
+            cfg_explicit_empty
+                .server
+                .proxy_protocol_trusted_cidrs
+                .is_empty()
+        );
+    }
+
     #[test]
     fn dc_overrides_allow_string_and_array() {
         let toml = r#"
diff --git a/src/config/types.rs b/src/config/types.rs
index 240d2f1..2d204e2 100644
--- a/src/config/types.rs
+++ b/src/config/types.rs
@@ -1240,9 +1240,10 @@ pub struct ServerConfig {
 
     /// Trusted source CIDRs allowed to send incoming PROXY protocol headers.
     ///
-    /// When non-empty, connections from addresses outside this allowlist are
-    /// rejected before `src_addr` is applied.
-    #[serde(default)]
+    /// If this field is omitted in config, it defaults to trust-all CIDRs
+    /// (`0.0.0.0/0` and `::/0`). If it is explicitly set to an empty list,
+    /// all PROXY protocol headers are rejected.
+    #[serde(default = "default_proxy_protocol_trusted_cidrs")]
     pub proxy_protocol_trusted_cidrs: Vec<IpNetwork>,
 
     /// Port for the Prometheus-compatible metrics endpoint.
@@ -1287,7 +1288,7 @@ impl Default for ServerConfig {
             listen_tcp: None,
             proxy_protocol: false,
             proxy_protocol_header_timeout_ms: default_proxy_protocol_header_timeout_ms(),
-            proxy_protocol_trusted_cidrs: Vec::new(),
+            proxy_protocol_trusted_cidrs: default_proxy_protocol_trusted_cidrs(),
             metrics_port: None,
             metrics_listen: None,
             metrics_whitelist: default_metrics_whitelist(),
diff --git a/src/proxy/client.rs b/src/proxy/client.rs
index 0190e8e..0becac7 100644
--- a/src/proxy/client.rs
+++ b/src/proxy/client.rs
@@ -323,7 +323,7 @@ fn is_trusted_proxy_source(peer_ip: IpAddr, trusted: &[IpNetwork]) -> bool {
         let warned = EMPTY_PROXY_TRUST_WARNED.get_or_init(|| AtomicBool::new(false));
         if !warned.swap(true, Ordering::Relaxed) {
             warn!(
-                "PROXY protocol enabled but server.proxy_protocol_trusted_cidrs is empty; rejecting all PROXY headers by default"
+                "PROXY protocol enabled but server.proxy_protocol_trusted_cidrs is empty; rejecting all PROXY headers"
             );
         }
         return false;