Code:  int re_yyget_column  (yyscan_t yyscanner)
 {
     struct yyguts_t * yyg = (struct yyguts_t*)yyscanner;
         if (! YY_CURRENT_BUFFER)
             return 0;
     
    return yycolumn;
}

Vulnerability Type: DoS 
CWE ID: CWE-476
Summary: libyara/lexer.l in YARA 3.5.0 allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via a crafted rule that is mishandled in the yy_get_next_buffer function.
Commit Message: re_lexer: Make reading escape sequences more robust (#586)

* Add test for issue #503

* re_lexer: Make reading escape sequences more robust

This commit fixes parsing incomplete escape sequences at the end of a
regular expression and parsing things like \xxy (invalid hex digits)
which before were silently turned into (char)255.

Close #503

* Update re_lexer.c