diff --git a/webrtc/base/network.cc b/webrtc/base/network.cc
index 0018779470..c9ad181776 100644
--- a/webrtc/base/network.cc
+++ b/webrtc/base/network.cc
@@ -357,12 +357,34 @@ bool NetworkManagerBase::GetDefaultLocalAddress(int family,
     *ipaddr = default_local_ipv4_address_;
     return true;
   } else if (family == AF_INET6 && !default_local_ipv6_address_.IsNil()) {
-    *ipaddr = default_local_ipv6_address_;
+    Network* ipv6_network = GetNetworkFromAddress(default_local_ipv6_address_);
+    if (ipv6_network) {
+      // If the default ipv6 network's BestIP is different than
+      // default_local_ipv6_address_, use it instead.
+      // This is to prevent potential IP address leakage. See WebRTC bug 5376.
+      *ipaddr = ipv6_network->GetBestIP();
+    } else {
+      *ipaddr = default_local_ipv6_address_;
+    }
     return true;
   }
   return false;
 }
 
+Network* NetworkManagerBase::GetNetworkFromAddress(
+    const rtc::IPAddress& ip) const {
+  for (Network* network : networks_) {
+    const auto& ips = network->GetIPs();
+    if (std::find_if(ips.begin(), ips.end(),
+                     [ip](const InterfaceAddress& existing_ip) {
+                       return ip == static_cast<rtc::IPAddress>(existing_ip);
+                     }) != ips.end()) {
+      return network;
+    }
+  }
+  return nullptr;
+}
+
 BasicNetworkManager::BasicNetworkManager()
     : thread_(NULL), sent_first_update_(false), start_count_(0),
       ignore_non_default_routes_(false) {
diff --git a/webrtc/base/network.h b/webrtc/base/network.h
index ee22d5e573..7c328fffe9 100644
--- a/webrtc/base/network.h
+++ b/webrtc/base/network.h
@@ -160,6 +160,8 @@ class NetworkManagerBase : public NetworkManager {
  private:
   friend class NetworkTest;
 
+  Network* GetNetworkFromAddress(const rtc::IPAddress& ip) const;
+
   EnumerationPermission enumeration_permission_;
 
   NetworkList networks_;
diff --git a/webrtc/base/network_unittest.cc b/webrtc/base/network_unittest.cc
index 7133d8b405..d365477a07 100644
--- a/webrtc/base/network_unittest.cc
+++ b/webrtc/base/network_unittest.cc
@@ -1006,6 +1006,35 @@ TEST_F(NetworkTest, DefaultLocalAddress) {
   EXPECT_EQ(ip, GetLoopbackIP(AF_INET));
   EXPECT_TRUE(manager.GetDefaultLocalAddress(AF_INET6, &ip));
   EXPECT_EQ(ip, GetLoopbackIP(AF_INET6));
+
+  // More tests on GetDefaultLocalAddress with ipv6 addresses where the set
+  // default address may be different from the best IP address of any network.
+  InterfaceAddress ip1;
+  EXPECT_TRUE(IPFromString("abcd::1234:5678:abcd:1111",
+                           IPV6_ADDRESS_FLAG_TEMPORARY, &ip1));
+  // Create a network with a prefix of ip1.
+  Network ipv6_network("test_eth0", "Test NetworkAdapter", TruncateIP(ip1, 64),
+                       64);
+  IPAddress ip2;
+  EXPECT_TRUE(IPFromString("abcd::1234:5678:abcd:2222", &ip2));
+  ipv6_network.AddIP(ip1);
+  ipv6_network.AddIP(ip2);
+  BasicNetworkManager::NetworkList list(1, new Network(ipv6_network));
+  bool changed;
+  MergeNetworkList(manager, list, &changed);
+  // If the set default address is not in any network, GetDefaultLocalAddress
+  // should return it.
+  IPAddress ip3;
+  EXPECT_TRUE(IPFromString("abcd::1234:5678:abcd:3333", &ip3));
+  manager.set_default_local_addresses(GetLoopbackIP(AF_INET), ip3);
+  EXPECT_TRUE(manager.GetDefaultLocalAddress(AF_INET6, &ip));
+  EXPECT_EQ(ip3, ip);
+  // If the set default address is in a network, GetDefaultLocalAddress will
+  // return the best IP in that network.
+  manager.set_default_local_addresses(GetLoopbackIP(AF_INET), ip2);
+  EXPECT_TRUE(manager.GetDefaultLocalAddress(AF_INET6, &ip));
+  EXPECT_EQ(static_cast<IPAddress>(ip1), ip);
+
   manager.StopUpdating();
 }