Reject NaN with payload while parsing JSON

This commit drops support for parsing NaN with payload in JSON like
`NaN123` and fixes CVE-2024-53427. Other JSON extensions like `NaN` and
`Infinity` are still supported. Fixes #3023, fixes #3196, fixes #3246.

src/jv.c

@@ -585,6 +585,11 @@ static jv jvp_literal_number_new(const char * literal) {
     return JV_INVALID;
   }
   if (decNumberIsNaN(&n->num_decimal)) {
+    // Reject NaN with payload.
+    if (n->num_decimal.digits > 1 || *n->num_decimal.lsu != 0) {
+      jv_mem_free(n);
+      return JV_INVALID;
+    }
     jv_mem_free(n);
     return jv_number(NAN);
   }

tests/jq.test

@@ -2110,11 +2110,17 @@ tojson | fromjson
 {"a":nan}
 {"a":null}
 
-# also "nan with payload" #2985
-if have_decnum then fromjson else nan end | isnan
-"nan1234"
+# NaN with payload is not parsed
+.[] | try (fromjson | isnan) catch .
+["NaN","-NaN","NaN1","NaN10","NaN100","NaN1000","NaN10000","NaN100000"]
 true
-
+true
+"Invalid numeric literal at EOF at line 1, column 4 (while parsing 'NaN1')"
+"Invalid numeric literal at EOF at line 1, column 5 (while parsing 'NaN10')"
+"Invalid numeric literal at EOF at line 1, column 6 (while parsing 'NaN100')"
+"Invalid numeric literal at EOF at line 1, column 7 (while parsing 'NaN1000')"
+"Invalid numeric literal at EOF at line 1, column 8 (while parsing 'NaN10000')"
+"Invalid numeric literal at EOF at line 1, column 9 (while parsing 'NaN100000')"
 
 # calling input/0, or debug/0 in a test doesn't crash jq
 

tests/shtest

@@ -669,13 +669,6 @@ if ! x=$($JQ -cn "$(printf '[\r\n1,# comment\r\n2,# comment\\\r\ncomment\r\n3\r\
   exit 1
 fi
 
-# CVE-2023-50268: No stack overflow comparing a nan with a large payload
-if $JQ -ne 'have_decnum'; then
-  $VALGRIND $Q $JQ '1 != .' <<\EOF >/dev/null
-  Nan4000
-EOF
-fi
-
 # Allow passing the inline jq script before -- #2919
 if ! r=$($JQ --args -rn -- '$ARGS.positional[0]' bar) || [ "$r" != bar ]; then
     echo "passing the inline script after -- didn't work"