CVE-2026-55195: CWE-409: Improper Handling of Highly Compressed Data (Data Amplification) in miurahr py7zr
py7zr versions prior to 1.1.3 contain a vulnerability in the Worker.decompress() function where the total decompressed size of archive entries is not tracked. This allows a crafted 7z archive with a small compressed size to decompress into a much larger size, potentially exhausting disk or memory resources. The issue is fixed in version 1.1.3.
AI Analysis
Technical Summary
The py7zr Python library before version 1.1.3 improperly handles highly compressed data during decompression by not tracking the total decompressed size in Worker.decompress(). This allows an attacker to craft a small 7z archive that decompresses to a significantly larger size, causing resource exhaustion such as disk or memory exhaustion. This vulnerability is classified under CWE-409 (Improper Handling of Highly Compressed Data). The issue is resolved in py7zr version 1.1.3.
Potential Impact
An attacker can supply a maliciously crafted 7z archive that decompresses to a much larger size than the compressed input, leading to exhaustion of system disk or memory resources during extraction. This can cause denial of service or system instability on affected systems using vulnerable py7zr versions.
Mitigation Recommendations
Upgrade py7zr to version 1.1.3 or later where this issue is fixed. No other mitigation or temporary workaround is indicated.
CVE-2026-55195: CWE-409: Improper Handling of Highly Compressed Data (Data Amplification) in miurahr py7zr
Description
py7zr versions prior to 1.1.3 contain a vulnerability in the Worker.decompress() function where the total decompressed size of archive entries is not tracked. This allows a crafted 7z archive with a small compressed size to decompress into a much larger size, potentially exhausting disk or memory resources. The 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
The py7zr Python library before version 1.1.3 improperly handles highly compressed data during decompression by not tracking the total decompressed size in Worker.decompress(). This allows an attacker to craft a small 7z archive that decompresses to a significantly larger size, causing resource exhaustion such as disk or memory exhaustion. This vulnerability is classified under CWE-409 (Improper Handling of Highly Compressed Data). The issue is resolved in py7zr version 1.1.3.
Potential Impact
An attacker can supply a maliciously crafted 7z archive that decompresses to a much larger size than the compressed input, leading to exhaustion of system disk or memory resources during extraction. This can cause denial of service or system instability on affected systems using vulnerable py7zr versions.
Mitigation Recommendations
Upgrade py7zr to version 1.1.3 or later where this issue is fixed. No other mitigation or temporary workaround is indicated.
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: 07/08/2026, 20:58:44 UTC
Last updated: 07/08/2026, 20:58:44 UTC
Views: 2
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