diff --git a/cmake/abseil-cpp.cmake b/cmake/abseil-cpp.cmake
index e40ea5c..ee1b905 100644
--- a/cmake/abseil-cpp.cmake
+++ b/cmake/abseil-cpp.cmake
@@ -16,8 +16,8 @@ set(workdir "${CMAKE_BINARY_DIR}/_deps/absl-populate")
 
 set(SAPI_ABSL_GIT_REPOSITORY https://github.com/abseil/abseil-cpp.git
                              CACHE STRING "")
-set(SAPI_ABSL_GIT_TAG b315753c0b8b4aa4e3e1479375eddb518393bab6
-                      CACHE STRING "") # 2021-02-18
+set(SAPI_ABSL_GIT_TAG d96e287417766deddbff2d01b96321288c59491e
+                      CACHE STRING "") # 2021-04-23
 set(SAPI_ABSL_SOURCE_DIR "${CMAKE_BINARY_DIR}/_deps/absl-src" CACHE STRING "")
 set(SAPI_ABSL_BINARY_DIR "${CMAKE_BINARY_DIR}/_deps/absl-build" CACHE STRING "")
 
diff --git a/cmake/protobuf.cmake b/cmake/protobuf.cmake
index 2686ee3..9f120fe 100644
--- a/cmake/protobuf.cmake
+++ b/cmake/protobuf.cmake
@@ -17,7 +17,7 @@ set(workdir "${CMAKE_BINARY_DIR}/_deps/protobuf-populate")
 set(SAPI_PROTOBUF_GIT_REPOSITORY
   https://github.com/protocolbuffers/protobuf.git
   CACHE STRING "")
-set(SAPI_PROTOBUF_GIT_TAG v3.14.0 CACHE STRING "") # 2020-11-14
+set(SAPI_PROTOBUF_GIT_TAG v3.15.8 CACHE STRING "") # 2021-04-08
 set(SAPI_PROTOBUF_SOURCE_DIR "${CMAKE_BINARY_DIR}/_deps/protobuf-src"
                              CACHE STRING "")
 set(SAPI_PROTOBUF_BINARY_DIR "${CMAKE_BINARY_DIR}/_deps/protobuf-build"
diff --git a/sandboxed_api/bazel/sapi_deps.bzl b/sandboxed_api/bazel/sapi_deps.bzl
index 3633357..80a2387 100644
--- a/sandboxed_api/bazel/sapi_deps.bzl
+++ b/sandboxed_api/bazel/sapi_deps.bzl
@@ -25,25 +25,27 @@ def sapi_deps():
     maybe(
         http_archive,
         name = "bazel_skylib",
-        sha256 = "154f4063d96a4e47b17a917108eaabdfeb4ef08383795cf936b3be6f8179c9fc",  # 2020-04-15
-        strip_prefix = "bazel-skylib-560d7b2359aecb066d81041cb532b82d7354561b",
-        url = "https://github.com/bazelbuild/bazel-skylib/archive/560d7b2359aecb066d81041cb532b82d7354561b.zip",
+        urls = [
+            "https://github.com/bazelbuild/bazel-skylib/releases/download/1.0.3/bazel-skylib-1.0.3.tar.gz",
+            "https://mirror.bazel.build/github.com/bazelbuild/bazel-skylib/releases/download/1.0.3/bazel-skylib-1.0.3.tar.gz",
+        ],
+        sha256 = "1c531376ac7e5a180e0237938a2536de0c54d93f5c278634818e0efc952dd56c",  # 2020-08-27
     )
 
     # Abseil
     maybe(
         http_archive,
         name = "com_google_absl",
-        sha256 = "e140988c4d3c22f829a3095f0d34a0783aa2f8829556283f10b8eb63a9428b19",  # 2021-02-19
-        strip_prefix = "abseil-cpp-b315753c0b8b4aa4e3e1479375eddb518393bab6",
-        urls = ["https://github.com/abseil/abseil-cpp/archive/b315753c0b8b4aa4e3e1479375eddb518393bab6.zip"],
+        sha256 = "7192966b3ca413e7f7f141fac24725571d457f608cb3fc1182167006f50f5155",  # 2021-04-23
+        strip_prefix = "abseil-cpp-d96e287417766deddbff2d01b96321288c59491e",
+        urls = ["https://github.com/abseil/abseil-cpp/archive/d96e287417766deddbff2d01b96321288c59491e.zip"],
     )
     maybe(
         http_archive,
         name = "com_google_absl_py",
-        sha256 = "6ace3cd8921804aaabc37970590edce05c6664901cc98d30010d09f2811dc56f",  # 2019-10-25
-        strip_prefix = "abseil-py-06edd9c20592cec39178b94240b5e86f32e19768",
-        urls = ["https://github.com/abseil/abseil-py/archive/06edd9c20592cec39178b94240b5e86f32e19768.zip"],
+        sha256 = "3d0278d88bbd52993f381d1e20887fa30f0556f6263b3f7bfcad62c69f39b38e",  # 2021-03-09
+        strip_prefix = "abseil-py-9954557f9df0b346a57ff82688438c55202d2188",
+        urls = ["https://github.com/abseil/abseil-py/archive/9954557f9df0b346a57ff82688438c55202d2188.zip"],
     )
 
     # Abseil-py dependency for Python 2/3 compatiblity
@@ -51,12 +53,9 @@ def sapi_deps():
         http_archive,
         name = "six_archive",
         build_file = "@com_google_sandboxed_api//sandboxed_api:bazel/external/six.BUILD",
-        sha256 = "d16a0141ec1a18405cd4ce8b4613101da75da0e9a7aec5bdd4fa804d0e0eba73",  # 2018-12-10
-        strip_prefix = "six-1.12.0",
-        urls = [
-            "https://mirror.bazel.build/pypi.python.org/packages/source/s/six/six-1.12.0.tar.gz",
-            "https://pypi.python.org/packages/source/s/six/six-1.12.0.tar.gz",
-        ],
+        sha256 = "30639c035cdb23534cd4aa2dd52c3bf48f06e5f4a941509c8bafd8ce11080259",  # 2020-05-21
+        strip_prefix = "six-1.15.0",
+        urls = ["https://pypi.python.org/packages/source/s/six/six-1.15.0.tar.gz"],
     )
 
     # gflags
@@ -83,9 +82,9 @@ def sapi_deps():
     maybe(
         http_archive,
         name = "com_google_protobuf",
-        sha256 = "bf0e5070b4b99240183b29df78155eee335885e53a8af8683964579c214ad301",  # 2020-11-14
-        strip_prefix = "protobuf-3.14.0",
-        urls = ["https://github.com/protocolbuffers/protobuf/archive/v3.14.0.zip"],
+        sha256 = "dd513a79c7d7e45cbaeaf7655289f78fd6b806e52dbbd7018ef4e3cf5cff697a",  # 2021-04-08
+        strip_prefix = "protobuf-3.15.8",
+        urls = ["https://github.com/protocolbuffers/protobuf/archive/v3.15.8.zip"],
     )
 
     # libcap
diff --git a/sandboxed_api/sandbox2/network_proxy/client.h b/sandboxed_api/sandbox2/network_proxy/client.h
index 7318993..8026679 100644
--- a/sandboxed_api/sandbox2/network_proxy/client.h
+++ b/sandboxed_api/sandbox2/network_proxy/client.h
@@ -16,6 +16,7 @@
 #define SANDBOXED_API_SANDBOX2_NETWORK_PROXY_CLIENT_H_
 
 #include <netinet/in.h>
+#include <signal.h>
 
 #include "absl/status/status.h"
 #include "absl/synchronization/mutex.h"
@@ -32,10 +33,9 @@ class NetworkProxyClient {
   NetworkProxyClient(const NetworkProxyClient&) = delete;
   NetworkProxyClient& operator=(const NetworkProxyClient&) = delete;
 
-  // Establishes a new network connection.
-  // Semantic is similar to a regular connect() call.
-  // Arguments are sent to network proxy server, which sends back a connected
-  // socket.
+  // Establishes a new network connection with semantics similar to a regular
+  // connect() call. Arguments are sent to network proxy server, which sends
+  // back a connected socket.
   absl::Status Connect(int sockfd, const struct sockaddr* addr,
                        socklen_t addrlen);
   // Same as Connect, but with same API as regular connect() call.
@@ -53,10 +53,10 @@ class NetworkProxyClient {
 class NetworkProxyHandler {
  public:
   // Installs the handler that redirects connect() syscalls to the trap
-  // function. This function exchange data with NetworkProxyServer that checks
+  // function. This function exchanges data with NetworkProxyServer that checks
   // if this connection is allowed and sends the connected socket to us.
-  // In other words, this function just use NetworkProxyClient class.
   static absl::Status InstallNetworkProxyHandler(NetworkProxyClient* npc);
+
   void ProcessSeccompTrap(int nr, siginfo_t* info, void* void_context);
 
  private:
diff --git a/sandboxed_api/sandbox2/network_proxy/server.cc b/sandboxed_api/sandbox2/network_proxy/server.cc
index b9c0630..5b16ad2 100644
--- a/sandboxed_api/sandbox2/network_proxy/server.cc
+++ b/sandboxed_api/sandbox2/network_proxy/server.cc
@@ -16,6 +16,7 @@
 
 #include <arpa/inet.h>
 #include <netinet/in.h>
+#include <signal.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/types.h>