CVE-2026-55195: CWE-409: Improper Handling of Highly Compressed Data (Data Amplification) in miurahr py7zr
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.
AI Analysis
Technical Summary
CVE-2026-55195 describes a vulnerability in the py7zr library before version 1.1.3 where the Worker.decompress() function extracted archive entries without monitoring the total decompressed size. This improper handling of highly compressed data (CWE-409) enables a crafted .7z archive to expand disproportionately during decompression, leading to resource exhaustion such as disk or memory depletion. The vulnerability has a CVSS 4.0 score of 8.7 (high severity). The issue is resolved in py7zr version 1.1.3.
Potential Impact
An attacker can supply a maliciously crafted 7zip archive that decompresses to a very large size relative to its compressed size, causing the decompression process to consume excessive disk space or memory. This can lead to denial of service conditions due to resource exhaustion on the system performing the extraction.
Mitigation Recommendations
Upgrade py7zr to version 1.1.3 or later, where this issue is fixed by tracking the total decompressed size during extraction. No other mitigations are specified. Patch status is not explicitly stated but the fix is included in version 1.1.3.
CVE-2026-55195: CWE-409: Improper Handling of Highly Compressed Data (Data Amplification) in miurahr py7zr
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.
CVSS v4.0
Score 8.7high
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-55195 describes a vulnerability in the py7zr library before version 1.1.3 where the Worker.decompress() function extracted archive entries without monitoring the total decompressed size. This improper handling of highly compressed data (CWE-409) enables a crafted .7z archive to expand disproportionately during decompression, leading to resource exhaustion such as disk or memory depletion. The vulnerability has a CVSS 4.0 score of 8.7 (high severity). The issue is resolved in py7zr version 1.1.3.
Potential Impact
An attacker can supply a maliciously crafted 7zip archive that decompresses to a very large size relative to its compressed size, causing the decompression process to consume excessive disk space or memory. This can lead to denial of service conditions due to resource exhaustion on the system performing the extraction.
Mitigation Recommendations
Upgrade py7zr to version 1.1.3 or later, where this issue is fixed by tracking the total decompressed size during extraction. No other mitigations are specified. Patch status is not explicitly stated but the fix is included in version 1.1.3.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-16T15:20:43.087Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a4eb690c9d9e3dbe3b6872f
Added to database: 07/08/2026, 20:44:00 UTC
Last enriched: 07/16/2026, 10:11:13 UTC
Last updated: 08/22/2026, 10:52:10 UTC
Views: 74
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