--- src/corelib/tools/qstring.cpp
+++ src/corelib/tools/qstring.cpp
@@ -3342,6 +3342,7 @@ QString QString::fromUtf8(const char *st
     result.resize(size); // worst case
     ushort *qch = result.d->data;
     uint uc = 0;
+    uint min_uc = 0;
     int need = 0;
     int error = -1;
     uchar ch;
@@ -3359,6 +3360,12 @@ QString QString::fromUtf8(const char *st
                         ushort low = uc%0x400 + 0xdc00;
                         *qch++ = high;
                         *qch++ = low;
+                    } else if ((uc < min_uc) || (uc >= 0xd800 && uc <= 0xdfff) || (uc >= 0xfffe)) {
+			// overlong seqence, UTF16 surrogate or BOM
+                        i = error;
+                        qch = addOne(qch, result);
+                        *qch++ = 0xdbff;
+                        *qch++ = 0xde00 + ((uchar)str[i]);
                     } else {
                         *qch++ = uc;
                     }
@@ -3381,14 +3388,17 @@ QString QString::fromUtf8(const char *st
                 uc = ch & 0x1f;
                 need = 1;
                 error = i;
+                min_uc = 0x80;
             } else if ((ch & 0xf0) == 0xe0) {
                 uc = ch & 0x0f;
                 need = 2;
                 error = i;
+                min_uc = 0x800;
             } else if ((ch&0xf8) == 0xf0) {
                 uc = ch & 0x07;
                 need = 3;
                 error = i;
+                min_uc = 0x10000;
             } else {
                 // Error
                 qch = addOne(qch, result);
--- src/corelib/codecs/qutfcodec.cpp
+++ src/corelib/codecs/qutfcodec.cpp
@@ -117,15 +117,19 @@ QString QUtf8Codec::convertToUnicode(con
     bool headerdone = false;
     QChar replacement = QChar::ReplacementCharacter;
     int need = 0;
+    int error = -1;
     uint uc = 0;
+    uint min_uc = 0;
     if (state) {
         if (state->flags & IgnoreHeader)
             headerdone = true;
         if (state->flags & ConvertInvalidToNull)
             replacement = QChar::Null;
         need = state->remainingChars;
-        if (need)
+        if (need) {
             uc = state->state_data[0];
+            min_uc = state->state_data[1];
+        }
     }
     if (!headerdone && len > 3
         && (uchar)chars[0] == 0xef && (uchar)chars[1] == 0xbb && (uchar)chars[2] == 0xbf) {
@@ -142,7 +146,7 @@ QString QUtf8Codec::convertToUnicode(con
     int invalid = 0;
 
     for (int i=0; i<len; i++) {
-        ch = *chars++;
+        ch = chars[i];
         if (need) {
             if ((ch&0xc0) == 0x80) {
                 uc = (uc << 6) | (ch & 0x3f);
@@ -153,14 +157,27 @@ QString QUtf8Codec::convertToUnicode(con
                         uc -= 0x10000;
                         unsigned short high = uc/0x400 + 0xd800;
                         unsigned short low = uc%0x400 + 0xdc00;
+
+                        // resize if necessary
+                        long where = qch - result.unicode();
+                        if (where + 2 >= result.size()) {
+                            result.resize(where + 2);
+                            qch = result.data() + where;
+                        }
+
                         *qch++ = QChar(high);
                         *qch++ = QChar(low);
+                    } else if ((uc < min_uc) || (uc >= 0xd800 && uc <= 0xdfff) || (uc >= 0xfffe)) {
+                        // error
+                        *qch++ = QChar::ReplacementCharacter;
+                        ++invalid;
                     } else {
                         *qch++ = uc;
                     }
                 }
             } else {
                 // error
+                i = error;
                 *qch++ = QChar::ReplacementCharacter;
                 ++invalid;
                 need = 0;
@@ -171,12 +188,22 @@ QString QUtf8Codec::convertToUnicode(con
             } else if ((ch & 0xe0) == 0xc0) {
                 uc = ch & 0x1f;
                 need = 1;
+                error = i;
+                min_uc = 0x80;
             } else if ((ch & 0xf0) == 0xe0) {
                 uc = ch & 0x0f;
                 need = 2;
+                error = i;
+                min_uc = 0x800;
             } else if ((ch&0xf8) == 0xf0) {
                 uc = ch & 0x07;
                 need = 3;
+                error = i;
+                min_uc = 0x10000;
+            } else {
+                // error
+                *qch++ = QChar::ReplacementCharacter;
+                ++invalid;
             }
         }
     }
@@ -187,6 +214,7 @@ QString QUtf8Codec::convertToUnicode(con
         if (headerdone)
             state->flags |= IgnoreHeader;
         state->state_data[0] = need ? uc : 0;
+        state->state_data[1] = need ? min_uc : 0;
     }
     return result;
 }