diff --git a/src/ProjLib/ProjLib_Cylinder.cxx b/src/ProjLib/ProjLib_Cylinder.cxx
index e3a37e980f..5c40eeac91 100644
--- a/src/ProjLib/ProjLib_Cylinder.cxx
+++ b/src/ProjLib/ProjLib_Cylinder.cxx
@@ -134,6 +134,12 @@ static gp_Pnt2d EvalPnt2d( const gp_Pnt& P, const gp_Cylinder& Cy )
 
 void  ProjLib_Cylinder::Project(const gp_Lin& L)
 {
+  // Check the line is parallel to the axis of cylinder.
+  // In other cases, the projection is wrong.
+  if (L.Direction().XYZ().CrossSquareMagnitude(myCylinder.Position().Direction().XYZ()) >
+      Precision::Angular() * Precision::Angular())
+    return;
+
   myType = GeomAbs_Line;
 
   gp_Pnt2d P2d = EvalPnt2d(L.Location(),myCylinder);
@@ -157,23 +163,26 @@ void  ProjLib_Cylinder::Project(const gp_Lin& L)
 
 void  ProjLib_Cylinder::Project(const gp_Circ& C)
 {
+  // Check the circle's normal is parallel to the axis of cylinder.
+  // In other cases, the projection is wrong.
+  const gp_Ax3& aCylPos = myCylinder.Position();
+  const gp_Ax2& aCircPos = C.Position();
+  if (aCylPos.Direction().XYZ().CrossSquareMagnitude(aCircPos.Direction().XYZ()) >
+      Precision::Angular() * Precision::Angular())
+    return;
+
   myType = GeomAbs_Line;
 
-  gp_Dir ZCyl = myCylinder.Position().XDirection().Crossed
-    (myCylinder.Position().YDirection());
-  gp_Dir ZCir = C.Position().XDirection().Crossed
-    (C.Position().YDirection());
+  gp_Dir ZCyl = aCylPos.XDirection().Crossed(aCylPos.YDirection());
 
-  Standard_Real U = myCylinder.Position().XDirection()
-    .AngleWithRef(C.Position().XDirection(), ZCyl);
+  Standard_Real U = aCylPos.XDirection().AngleWithRef(aCircPos.XDirection(), ZCyl);
 
   gp_Vec OP( myCylinder.Location(),C.Location());
-  Standard_Real V = OP.Dot(gp_Vec(myCylinder.Position().Direction()));
-
+  Standard_Real V = OP.Dot(gp_Vec(aCylPos.Direction()));
 
   gp_Pnt2d P2d1 (U, V);
   gp_Dir2d D2d;
-  if ( ZCyl.Dot(ZCir) > 0.) 
+  if ( ZCyl.Dot(aCircPos.Direction()) > 0.) 
     D2d.SetCoord(1., 0.);
   else
     D2d.SetCoord(-1., 0.);
diff --git a/src/ProjLib/ProjLib_ProjectedCurve.cxx b/src/ProjLib/ProjLib_ProjectedCurve.cxx
index e78f04f9b8..8dd1817065 100644
--- a/src/ProjLib/ProjLib_ProjectedCurve.cxx
+++ b/src/ProjLib/ProjLib_ProjectedCurve.cxx
@@ -607,6 +607,8 @@ void ProjLib_ProjectedCurve::Load(const Handle(Adaptor3d_HCurve)& C)
   {
     // Use advanced analytical projector if base analytical projection failed.
     ProjLib_ComputeApprox Comp( myCurve, mySurface, myTolerance);
+    if (Comp.Bezier().IsNull() && Comp.BSpline().IsNull())
+      return; // advanced projector has been failed too
     myResult.Done();
 
     // set the type
diff --git a/tests/bugs/modalg_6/bug27677 b/tests/bugs/modalg_6/bug27677
new file mode 100644
index 0000000000..faa01cc91d
--- /dev/null
+++ b/tests/bugs/modalg_6/bug27677
@@ -0,0 +1,28 @@
+puts "================"
+puts "OCC27677"
+puts "================"
+puts ""
+#######################################################################
+# Incorrect CUT of a solid by semi-infinite solid
+#######################################################################
+
+restore [locate_data_file bug27677_solid_halfspace.brep] s
+restore [locate_data_file bug27677_real_frame_shape.brep] f
+
+bop s f
+boptuc result
+
+# Check result validity.
+checkshape result
+
+# Check number of topological entities in the result.
+checknbshapes result -solid 1 -shell 1 -face 11 -wire 12 -edge 32 -vertex 22
+
+# Check result area.
+checkprops result -s 2.82114
+
+smallview
+don result
+fit
+
+checkview -screenshot -2d -path ${imagedir}/${test_image}.png