# CVE-2026-124586: Tencent RapidJSON out-of-bounds read in floating-point parsing

Source: https://junglewise.ai/threats/cve-2026-124586-a-vulnerability-was-determined-in-tencent-rapidjson-1-1-0  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-09. Updated: 2026-11-09  
License: CC BY 4.0 with a link back

CVE-2026-124586 · Severity: high · CVSS 7.3 · Published 2026-11-09

RapidJSON is a widely-used C++ JSON parsing library. A flaw in full-precision floating-point number parsing allows attackers to trigger an out-of-bounds memory read by crafting malicious JSON input, potentially leading to information disclosure or application crash. The vulnerability can be exploited remotely and has been publicly disclosed.

Vendors: [Tencent](https://junglewise.ai/threats/vendors/tencent).

## Quick answers

**Is CVE-2026-124586 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-124586 being exploited in the wild.

**How severe is CVE-2026-124586?** High severity, with a CVSS score of 7.3, published 9 November 2026.

**Which products and versions are affected?** Tencent RapidJSON 1.1.0.

**Is there a fix for CVE-2026-124586?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-124586 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-124586?** Check whether you run Tencent RapidJSON at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

An integer underflow in the decimalPosition variable during full-precision float parsing causes an out-of-bounds array access in the GetCachedPowerByIndex() function within include/rapidjson/internal/diyfp.h. When parsing floating-point numbers with the kParseFullPrecisionFlag set, a specially crafted input (such as "1.1" followed by 192 zeros) causes decimalPosition to underflow, resulting in an invalid array index far exceeding the bounds of the kCachedPowers_F array. This enables remote out-of-bounds read without authentication.

## Affected products

- Tencent RapidJSON 1.1.0

## Timeline

- 2026-10-16: disclosed: Issue #2405 reported on GitHub
- 2026-11-09: advisory

## References

- [https://github.com/Tencent/rapidjson/](https://github.com/Tencent/rapidjson/)
- [https://github.com/Tencent/rapidjson/issues/2405](https://github.com/Tencent/rapidjson/issues/2405)

## Related threats

- [Tencent RapidJSON out-of-bounds read in string stream parsing](https://junglewise.ai/threats/cve-2026-116620-a-security-vulnerability-has-been-detected-in-tencent-rapidjson)