py7zr: Decompression bomb (zip bomb) denial of service via unchecked extraction size
Priority HIGH 77CWE-409Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- —
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub.
Summary
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.
Why it matters now
Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00321 25th percentileScored 2026-11-07
Fix Fixed py7zr (miurahr): 1.1.3py7zr (PyPI): 1.1.3
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| miurahr | py7zr | before 1.1.3 | 1.1.3 | Patch available | CNA |
| — | py7zr (PyPI) | before 1.1.3 | 1.1.3 | Patch available | GHSA-gjrg-mpp7-g774 |
- py7zr Vendormiurahr Affected before 1.1.3 Fixed in 1.1.3 Patch available CNA
- py7zr (PyPI) Vendor— Affected before 1.1.3 Fixed in 1.1.3 Patch available GHSA-gjrg-mpp7-g774
Remediation
- Fix · CNA py7zr (miurahr) Fixed in 1.1.3
- Fix · GHSA-gjrg-mpp7-g774 py7zr (PyPI) Fixed in 1.1.3 Advisory →
Vendor assessments
Timeline
- 2026-10-02 Threatist record created from CVE-2026-55195
- 2026-10-03 Alias added: GHSA-gjrg-mpp7-g774
References
More miurahr vulnerabilities
- TI-2026-39886 py7zr: O(n^2) algorithmic complexity DoS in PackInfo._read() CVSS 4.0HIGH 8.7
- TI-2026-19237 py7zr: Arbitrary File Write Vulnerability CVSS 3.1HIGH 8.0
Sources
- CVE-2026-55195 · CVE Program
- CVE-2026-55195 · NVD
- FIRST EPSS
- GHSA-gjrg-mpp7-g774 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-55195 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences