diff --git a/lib/uri/common.rb b/lib/uri/common.rb
index ca38bec7ec..0c4064a67a 100644
--- a/lib/uri/common.rb
+++ b/lib/uri/common.rb
@@ -19,6 +19,8 @@ module URI
   Parser = RFC2396_Parser
   RFC3986_PARSER = RFC3986_Parser.new
   Ractor.make_shareable(RFC3986_PARSER) if defined?(Ractor)
+  RFC2396_PARSER = RFC2396_Parser.new
+  Ractor.make_shareable(RFC2396_PARSER) if defined?(Ractor)
 
   # URI::Parser.new
   DEFAULT_PARSER = Parser.new
diff --git a/lib/uri/generic.rb b/lib/uri/generic.rb
index 69698c4e2d..f7eed57924 100644
--- a/lib/uri/generic.rb
+++ b/lib/uri/generic.rb
@@ -1133,17 +1133,16 @@ module URI
       base.fragment=(nil)
 
       # RFC2396, Section 5.2, 4)
-      if !authority
-        base.set_path(merge_path(base.path, rel.path)) if base.path && rel.path
-      else
-        # RFC2396, Section 5.2, 4)
-        base.set_path(rel.path) if rel.path
+      if authority
+        base.set_userinfo(rel.userinfo)
+        base.set_host(rel.host)
+        base.set_port(rel.port || base.default_port)
+        base.set_path(rel.path)
+      elsif base.path && rel.path
+        base.set_path(merge_path(base.path, rel.path))
       end
 
       # RFC2396, Section 5.2, 7)
-      base.set_userinfo(rel.userinfo) if rel.userinfo
-      base.set_host(rel.host)         if rel.host
-      base.set_port(rel.port)         if rel.port
       base.query = rel.query       if rel.query
       base.fragment=(rel.fragment) if rel.fragment
 
diff --git a/lib/uri/version.rb b/lib/uri/version.rb
index f0aca586ac..c93c97cf6f 100644
--- a/lib/uri/version.rb
+++ b/lib/uri/version.rb
@@ -1,6 +1,6 @@
 module URI
   # :stopdoc:
-  VERSION_CODE = '001202'.freeze
+  VERSION_CODE = '001204'.freeze
   VERSION = VERSION_CODE.scan(/../).collect{|n| n.to_i}.join('.').freeze
   # :startdoc:
 end
diff --git a/test/uri/test_generic.rb b/test/uri/test_generic.rb
index 3897c3d6ee..4b5e12c0ef 100644
--- a/test/uri/test_generic.rb
+++ b/test/uri/test_generic.rb
@@ -164,6 +164,17 @@ class URI::TestGeneric < Test::Unit::TestCase
     # must be empty string to identify as path-abempty, not path-absolute
     assert_equal('', url.host)
     assert_equal('http:////example.com', url.to_s)
+
+    # sec-2957667
+    url = URI.parse('http://user:pass@example.com').merge('//example.net')
+    assert_equal('http://example.net', url.to_s)
+    assert_nil(url.userinfo)
+    url = URI.join('http://user:pass@example.com', '//example.net')
+    assert_equal('http://example.net', url.to_s)
+    assert_nil(url.userinfo)
+    url = URI.parse('http://user:pass@example.com') + '//example.net'
+    assert_equal('http://example.net', url.to_s)
+    assert_nil(url.userinfo)
   end
 
   def test_parse_scheme_with_symbols
@@ -256,6 +267,13 @@ class URI::TestGeneric < Test::Unit::TestCase
     assert_equal(u0, u1)
   end
 
+  def test_merge_authority
+    u = URI.parse('http://user:pass@example.com:8080')
+    u0 = URI.parse('http://new.example.org/path')
+    u1 = u.merge('//new.example.org/path')
+    assert_equal(u0, u1)
+  end
+
   def test_route
     url = URI.parse('http://hoge/a.html').route_to('http://hoge/b.html')
     assert_equal('b.html', url.to_s)