diff --git a/include/exiv2/value.hpp b/include/exiv2/value.hpp
index 64a8ca7..4e9f285 100644
--- a/include/exiv2/value.hpp
+++ b/include/exiv2/value.hpp
@@ -1658,11 +1658,13 @@ namespace Exiv2 {
         ok_ = true;
         return static_cast<long>(value_[n]);
     }
+// #55 crash when value_[n].first == LONG_MIN
+#define LARGE_INT 1000000
     // Specialization for rational
     template<>
     inline long ValueType<Rational>::toLong(long n) const
     {
-        ok_ = (value_[n].second != 0);
+        ok_ = (value_[n].second != 0 && -LARGE_INT < value_[n].first && value_[n].first < LARGE_INT);
         if (!ok_) return 0;
         return value_[n].first / value_[n].second;
     }
@@ -1670,7 +1672,7 @@ namespace Exiv2 {
     template<>
     inline long ValueType<URational>::toLong(long n) const
     {
-        ok_ = (value_[n].second != 0);
+        ok_ = (value_[n].second != 0 && value_[n].first < LARGE_INT);
         if (!ok_) return 0;
         return value_[n].first / value_[n].second;
     }
diff --git a/src/basicio.cpp b/src/basicio.cpp
index 1ede931..eac756f 100644
--- a/src/basicio.cpp
+++ b/src/basicio.cpp
@@ -990,6 +990,7 @@ namespace Exiv2 {
     DataBuf FileIo::read(long rcount)
     {
         assert(p_->fp_ != 0);
+        if ( (size_t) rcount > size() ) throw Error(57);
         DataBuf buf(rcount);
         long readCount = read(buf.pData_, buf.size_);
         buf.size_ = readCount;
diff --git a/src/image.cpp b/src/image.cpp
index 31b9b81..eeb1f37 100644
--- a/src/image.cpp
+++ b/src/image.cpp
@@ -399,7 +399,13 @@ namespace Exiv2 {
                                 ;

                 // if ( offset > io.size() ) offset = 0; // Denial of service?
-                DataBuf  buf(size*count + pad+20);  // allocate a buffer
+
+                // #55 memory allocation crash test/data/POC8
+                long long allocate = (long long) size*count + pad+20;
+                if ( allocate > (long long) io.size() ) {
+                    throw Error(57);
+                }
+                DataBuf  buf(allocate);  // allocate a buffer
                 std::memcpy(buf.pData_,dir.pData_+8,4);  // copy dir[8:11] into buffer (short strings)
                 if ( count*size > 4 ) {            // read into buffer
                     size_t   restore = io.tell();  // save