diff --git a/src/gui/image/qxbmhandler.cpp b/src/gui/image/qxbmhandler.cpp

index 414e8233..2824480b 100644

--- a/src/gui/image/qxbmhandler.cpp

+++ b/src/gui/image/qxbmhandler.cpp

@@ -154,7 +154,9 @@ static bool read_xbm_body(QIODevice *device, int w, int h, QImage *outImage)

     w = (w+7)/8;                                // byte width

     while (y < h) {                                // for all encoded bytes...

-        if (p) {                                // p = "0x.."

+        if (p && p < (buf + readBytes - 3)) {      // p = "0x.."

+            if (!isxdigit(p[2]) || !isxdigit(p[3]))

+                return false;

             *b++ = hex2byte(p+2);

             p += 2;

             if (++x == w && ++y < h) {