https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=6980

diff --git a/MagickCore/fx.c b/MagickCore/fx.c
index 0ac170667f447af038b285fb0add2ed07a2be97f..f18fabd40e7d0b8124819ffd8ed05eba43b4437d 100644 (file)
--- a/MagickCore/fx.c
+++ b/MagickCore/fx.c
@@ -1329,7 +1329,8 @@ static double FxGetSymbol(FxInfo *fx_info,const PixelChannel channel,
               alpha=FxEvaluateSubexpression(fx_info,channel,x,y,subexpression,
                 &depth,&beta,exception);
               i=(ssize_t) alpha;
-              p++;
+              if (*p != '\0')
+                p++;
             }
           if (*p == '.')
             p++;