Medium 5.1Published Sep 3, 2026

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

Updated under an hour ago (2026-10-19 06:30 UTC)

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It affects jetperch pymonocypher. Add what you run to find out whether that includes you.

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Every CVE for jetperch pymonocypher

Exploited in the last 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.

CVSS: 5.1 MEDIUM (v4.0, CNA)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
Weakness (CWE): CWE-122, CWE-787, CWE-1284
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: Sep 3, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

jetperch pymonocypher jetperch:pymonocypher (from the name)	before 4.0.2.8	CNA record

References

https://github.com/jetperch/pymonocypher/security/advisories/GHSA-8f95-v3jq-cj86x-refsource-confirm
https://github.com/jetperch/pymonocypher/commit/90ff5b13b13b5673c372e188f482d8c172e6ab86x-refsource-misc
https://github.com/jetperch/pymonocypher/releases/tag/v4.0.2.8x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.