# CVE-2026-53720

## Summary

- **CVE ID:** CVE-2026-53720
- **Severity:** MEDIUM
- **CVSS Score:** 5.1 (CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N)
- **CWE:** CWE-122, CWE-787, CWE-1284
- **Published:** Sep 3, 2026
- **Last Modified:** Sep 3, 2026

## Description

pymonocypher uses cython to wrap the Monocypher C library. Prior to version 4.0.2.8, the argon2i_32 implementation does not check the nb_blocks size. If the caller does not provide a sufficiently large buffer based on the API contract, then argon2i_32 will write past the end of the buffer and possibly corrupt the heap. This issue has been patched in version 4.0.2.8.

## Affected Products

- jetperch — pymonocypher (< 4.0.2.8)

## References

- [CNA](https://github.com/jetperch/pymonocypher/security/advisories/GHSA-8f95-v3jq-cj86)
- [CNA](https://github.com/jetperch/pymonocypher/commit/90ff5b13b13b5673c372e188f482d8c172e6ab86)
- [CNA](https://github.com/jetperch/pymonocypher/releases/tag/v4.0.2.8)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.13%
- **EPSS Percentile:** 2.6

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-09._