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

Quick assessment

Affected
jetperch pymonocypher
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

pymonocypher 使用 Cython 对 Monocypher C 库进行了封装。在 4.0.2.8 版本之前， 的实现未检查 的大小。如果调用方未按照 API 契约提供足够大的缓冲区，则 可能会在缓冲区末尾之外写入数据，从而可能导致堆内存损坏。该问题已在 4.0.2.8 版本中修复。

CVSS 5.1 · Medium

Possible ATT&CK Techniques 1 AI

T1069 · Permission Groups Discovery

Affected Version Matrix 1

VendorProduct Version RangeStatus
jetperch pymonocypher < 4.0.2.8 affected
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I. Basic Information for CVE-2026-53720

Vulnerability Information
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Vulnerability Title
pymonocypher: Potential heap buffer overflow on nb_blocks in argon2i_32 when provided buffer is too small
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
堆缓冲区溢出
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
jetperch pymonocypher < 4.0.2.8 -

II. Public POCs for CVE-2026-53720

# POC Description Source Link Shenlong Link
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III. Intelligence Information for CVE-2026-53720

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Patches & Fixes for CVE-2026-53720 (1)

Vendor Advisories for CVE-2026-53720 (1)

Vendor Pages for CVE-2026-53720 (1)

IV. Related Vulnerabilities

Same weakness: CWE-122

V. Comments for CVE-2026-53720

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