What’s Vulnerable › Vulnerabilities

CVE-2026-53720: pymonocypher: Potential heap buffer overflow on nb_blocks in argon2i_32 when provided buffer is too small

• Severity: medium (CVSS 5.1 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-03 · updated 2026-09-09
• Weakness: CWE-122

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: before 4.0.2.8

References

• https://github.com/jetperch/pymonocypher/commit/90ff5b13b13b5673c372e188f482d8c172e6ab86
• https://github.com/jetperch/pymonocypher/releases/tag/v4.0.2.8
• https://github.com/jetperch/pymonocypher/security/advisories/GHSA-8f95-v3jq-cj86

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