CVE-2026-53720: Jetperch Pymonocypher

Medium severity, CVSS 5.1. EPSS: 0.2% chance of exploitation in the next 30 days.

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 (fixed in 4.0.2.8)

Published 2026-09-03. Last modified 2026-09-09.