Version 1.1.28
File : libexslt/functions.c

Line no 114 , exsltFuncNewFunctionData is returning NULL in case of failure scenario.

Part of vesrion 1.1.28 code:  
if (func == NULL) {         /* Not yet present - copy it in */
        func = exsltFuncNewFunctionData();
        memcpy(func, data, sizeof(exsltFuncFunctionData));
   
Memcpy may crash in case of func=NULL.

So there shall be NULL check for func .

Recommended code part:
 if (func == NULL) {         /* Not yet present - copy it in */
      func = exsltFuncNewFunctionData();
      if (func == NULL)
          return;
      memcpy(func, data, sizeof(exsltFuncFunctionData));
 

I have attached patch for the fix for the failure scenario.