Prevent int underflow when parsing exponents #1261
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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
miloyip
reviewed
Jun 10, 2024
| // -(exp * 10 + 9) + expFrac >= INT_MIN | ||
| // <=> exp <= (expFrac - INT_MIN - 9) / 10 | ||
| RAPIDJSON_ASSERT(expFrac <= 0); | ||
| int maxExp = (expFrac + 2147483639) / 10; |
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This issue appears to have assigned CVE-2024-38517. |
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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