Automated rollback of commit 57d5ede3ec.

PiperOrigin-RevId: 526130253

src/google/protobuf/descriptor.cc

@@ -5927,8 +5927,13 @@ void DescriptorBuilder::BuildFieldOrExtension(const FieldDescriptorProto& proto,
         case FieldDescriptor::CPPTYPE_STRING:
           if (result->type() == FieldDescriptor::TYPE_BYTES) {
             std::string value;
-            absl::CUnescape(proto.default_value(), &value);
-            result->default_value_string_ = alloc.AllocateStrings(value);
+            if (absl::CUnescape(proto.default_value(), &value)) {
+              result->default_value_string_ = alloc.AllocateStrings(value);
+            } else {
+              AddError(result->full_name(), proto,
+                       DescriptorPool::ErrorCollector::DEFAULT_VALUE,
+                       "Invalid escaping in default value.");
+            }
           } else {
             result->default_value_string_ =
                 alloc.AllocateStrings(proto.default_value());

src/google/protobuf/descriptor_unittest.cc

@@ -4548,6 +4548,12 @@ TEST_F(ValidationErrorTest, InvalidDefaults) {
       "  field { name: \"corge\" number: 6 label: LABEL_REPEATED type: "
       "TYPE_INT32"
       "          default_value: \"1\" }"
+
+      // Invalid CEscaped bytes default.
+      "  field { name: \"bytes_default\" number: 7 label: LABEL_OPTIONAL "
+      "          type: TYPE_BYTES"
+      "          default_value: \"\\\\\" }"
+
       "}",
 
       "foo.proto: Foo.foo: DEFAULT_VALUE: Couldn't parse default value "
@@ -4558,6 +4564,8 @@ TEST_F(ValidationErrorTest, InvalidDefaults) {
       "foo.proto: Foo.moo: DEFAULT_VALUE: Messages can't have default values.\n"
       "foo.proto: Foo.corge: DEFAULT_VALUE: Repeated fields can't have default "
       "values.\n"
+      "foo.proto: Foo.bytes_default: DEFAULT_VALUE: Invalid escaping in "
+      "default value.\n"
       // This ends up being reported later because the error is detected at
       // cross-linking time.
       "foo.proto: Foo.mooo: DEFAULT_VALUE: Messages can't have default "