PYSEC-2026-3000
pymonocypher: Potential heap buffer overflow on nb_blocks in argon2i_32 when provided buffer is too small
Quick fix
PYSEC-2026-3000 — pymonocypher: upgrade to the fixed version with the command below.
pip install --upgrade 'pymonocypher>=4.0.2.8'Details
### Impact 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.
### Patches Fixed in 4.0.2.8, which now verifies that nb_blocks is large enough. See [90ff5b1](https://github.com/jetperch/pymonocypher/commit/90ff5b13b13b5673c372e188f482d8c172e6ab86).
### Workarounds Provide a correctly sized nb_blocks buffer.
pymonocypher thanks Haris (hextheshadow) for the vulnerability report, details, and recommended fix.
Are you affected?
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Affected packages
References
- https://github.com/jetperch/pymonocypher/security/advisories/GHSA-8f95-v3jq-cj86[WEB]
- https://github.com/jetperch/pymonocypher/commit/90ff5b13b13b5673c372e188f482d8c172e6ab86[WEB]
- https://github.com/jetperch/pymonocypher[PACKAGE]
- https://pypi.org/project/pymonocypher[PACKAGE]
- https://github.com/advisories/GHSA-8f95-v3jq-cj86[ADVISORY]
- https://nvd.nist.gov/vuln/detail/CVE-2026-53720[ADVISORY]