CVE-2024-38517 (published 2024-07-09T19:15Z)

Tencent RapidJSON is vulnerable to privilege escalation due to an integer underflow in the `GenericReader::ParseNumber()` function of `include/rapidjson/reader.h` when parsing JSON text from a stream. An attacker needs to send the victim a crafted file which needs to be opened; this triggers the integer underflow vulnerability (when the file is parsed), leading to elevation of privilege.


Weakness information:
cwe_id: NVD-CWE-noinfo
cwe_name: Insufficient Information
description: There is insufficient information about the issue to classify it; details are unkown or unspecified.
extended_description: Insufficient Information

Fix information:
repo_url: https://github.com/fmalita/rapidjson
commit_details: repo_url: https://github.com/fmalita/rapidjson
author: Florin Malita
author_date: 2018-05-15 22:48:07-04:00
msg: Prevent int underflow when parsing exponents

When parsing negative exponents, the current implementation takes
precautions for |exp| to not underflow int.

But that is not sufficient: later on [1], |exp + expFrac| is also
stored to an int - so we must ensure that the sum stays within int
representable values.

Update the exp clamping logic to take expFrac into account.

[1] https://github.com/Tencent/rapidjson/blob/master/include/rapidjson/reader.h#L1690
repository: repo_url: https://github.com/fmalita/rapidjson
repo_name: fmalita/rapidjson
description: A fast JSON parser/generator for C++ with both SAX/DOM style API
repo_language: C++
owner: fmalita
file_changes: filename: reader.h
change_type: ModificationType.MODIFY
diff: @@ -1632,9 +1632,18 @@ private:
             if (RAPIDJSON_LIKELY(s.Peek() >= '0' && s.Peek() <= '9')) {
                 exp = static_cast<int>(s.Take() - '0');
                 if (expMinus) {
+                    // (exp + expFrac) must not underflow int => we're detecting when -exp gets
+                    // dangerously close to INT_MIN (a pessimistic next digit 9 would push it into
+                    // underflow territory):
+                    //
+                    //        -(exp * 10 + 9) + expFrac >= INT_MIN
+                    //   <=>  exp <= (expFrac - INT_MIN - 9) / 10
+                    RAPIDJSON_ASSERT(expFrac <= 0);
+                    int maxExp = (expFrac + 2147483639) / 10;
+
                     while (RAPIDJSON_LIKELY(s.Peek() >= '0' && s.Peek() <= '9')) {
                         exp = exp * 10 + static_cast<int>(s.Take() - '0');
-                        if (exp >= 214748364) {                         // Issue #313: prevent overflow exponent
+                        if (RAPIDJSON_UNLIKELY(exp > maxExp)) {
                             while (RAPIDJSON_UNLIKELY(s.Peek() >= '0' && s.Peek() <= '9'))  // Consume the rest of exponent
                                 s.Take();
                         }

programming_language: C++
filename: readertest.cpp
change_type: ModificationType.MODIFY
diff: @@ -242,6 +242,7 @@ static void TestParseDouble() {
     TEST_DOUBLE(fullPrecision, "1e-214748363", 0.0);                                  // Maximum supported negative exponent
     TEST_DOUBLE(fullPrecision, "1e-214748364", 0.0);
     TEST_DOUBLE(fullPrecision, "1e-21474836311", 0.0);
+    TEST_DOUBLE(fullPrecision, "1.00000000001e-2147483638", 0.0);
     TEST_DOUBLE(fullPrecision, "0.017976931348623157e+310", 1.7976931348623157e+308); // Max double in another form
 
     // Since

programming_language: C++