CVE-2026-55195
HighCVSS 8.7Exploitation Probability (EPSS)
Low risk24th percentile - higher than 24% of all known CVEs
Summary
The py7zr library before version 1.1.3 does not track the total decompressed size, allowing a decompression bomb attack. A crafted .7z file (e.g., 15.6 KB) can expand to 100 MB, exhausting disk space or memory.
Risk Assessment
The organization is at risk of a denial-of-service (DoS) attack due to resource exhaustion when processing malicious 7z archives. This can disrupt applications relying on py7zr.
Recommendation
Immediately upgrade py7zr to version 1.1.3 or later. As a workaround, restrict processing of 7z archives from untrusted sources.
Other vulnerabilities in py7zr
See all- CVE-2026-55206High
The py7zr library prior to version 1.1.3 contains a denial-of-service vulnerability causing excessive CPU consumption during SevenZipFile initialization. The PackInfo._read() function in archiveinfo.py uses an O(n^2) cumulative sum pattern for attacker-controlled numstreams values parsed from archive headers, allowing a crafted .7z archive to trigger CPU exhaustion.
- CVE-2026-23879High
The py7zr library, used for compressing and decompressing 7zip archives, contains an arbitrary file write vulnerability in versions 1.1.2 and below. This allows attackers to create malicious archives that can restore symbolic links to arbitrary directories in the file system.
Original NVD description (English source)
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.