diff --git a/config.m4 b/config.m4
index b673ea99a..b4e16c8fa 100644
--- a/config.m4
+++ b/config.m4
@@ -448,10 +448,10 @@ if test "$PHP_MONGODB" != "no"; then
 
     if test "x$bundled_zlib" = "xyes"; then
       PHP_MONGODB_ZLIB_CFLAGS="$PHP_MONGODB_BUNDLED_CFLAGS $PHP_MONGODB_ZLIB_CFLAGS"
-      PHP_MONGODB_ADD_SOURCES([src/libmongoc/src/zlib-1.2.13/], $PHP_MONGODB_ZLIB_SOURCES, $PHP_MONGODB_ZLIB_CFLAGS)
-      PHP_MONGODB_ADD_INCLUDE([src/libmongoc/src/zlib-1.2.13/])
-      PHP_MONGODB_ADD_BUILD_DIR([src/libmongoc/src/zlib-1.2.13/])
-      AC_CONFIG_FILES([${ac_config_dir}/src/libmongoc/src/zlib-1.2.13/zconf.h])
+      PHP_MONGODB_ADD_SOURCES([src/libmongoc/src/zlib-1.3.1/], $PHP_MONGODB_ZLIB_SOURCES, $PHP_MONGODB_ZLIB_CFLAGS)
+      PHP_MONGODB_ADD_INCLUDE([src/libmongoc/src/zlib-1.3.1/])
+      PHP_MONGODB_ADD_BUILD_DIR([src/libmongoc/src/zlib-1.3.1/])
+      AC_CONFIG_FILES([${ac_config_dir}/src/libmongoc/src/zlib-1.3.1/zconf.h])
     fi
 
     if test "$PHP_MONGODB_CLIENT_SIDE_ENCRYPTION" = "yes"; then
diff --git a/scripts/update-submodule-sources.php b/scripts/update-submodule-sources.php
index ee295ca7e..124d04616 100644
--- a/scripts/update-submodule-sources.php
+++ b/scripts/update-submodule-sources.php
@@ -14,7 +14,7 @@
     'PHP_MONGODB_JSONSL_SOURCES' => 'src/libmongoc/src/libbson/src/jsonsl',
     'PHP_MONGODB_MONGOC_SOURCES' => 'src/libmongoc/src/libmongoc/src/mongoc',
     'PHP_MONGODB_UTF8PROC_SOURCES' => 'src/libmongoc/src/utf8proc-2.8.0',
-    'PHP_MONGODB_ZLIB_SOURCES' => 'src/libmongoc/src/zlib-1.2.13',
+    'PHP_MONGODB_ZLIB_SOURCES' => 'src/libmongoc/src/zlib-1.3.1',
     'PHP_MONGODB_MONGOCRYPT_SOURCES' => 'src/libmongocrypt/src',
     'PHP_MONGODB_MONGOCRYPT_CRYPTO_SOURCES' => 'src/libmongocrypt/src/crypto',
     'PHP_MONGODB_MONGOCRYPT_OS_POSIX_SOURCES' => 'src/libmongocrypt/src/os_posix',
diff --git a/src/LIBMONGOC_VERSION_CURRENT b/src/LIBMONGOC_VERSION_CURRENT
index d6201580e..bd9c63786 100644
--- a/src/LIBMONGOC_VERSION_CURRENT
+++ b/src/LIBMONGOC_VERSION_CURRENT
@@ -1 +1 @@
-1.27.4
+1.27.5
diff --git a/src/libmongoc b/src/libmongoc
index 3d1308b9f..01decf26c 160000
--- a/src/libmongoc
+++ b/src/libmongoc
@@ -1 +1 @@
-Subproject commit 3d1308b9fbc8411f3f62989bcfffc5790a7c63e4
+Subproject commit 01decf26c18b1b89d97d3b55317910a3460741ae