Grav: Decompression Bomb via ZipArchiver - Missing Extraction Limits
The advisory, in context
Summary
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.
Details
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);
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.
Proof of Concept
Step 1 - Create a zip bomb
# 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
Step 2 - Extract via ZipArchiver
$archiver = Archiver::create('zip');
$archiver->setArchive('/tmp/zipbomb.zip');
$archiver->extract('/tmp/extracted'); // ← no limits, fills disk
The server's disk fills with 10 GB of data. If the web root shares the disk, the site becomes unavailable (DoS).
Impact
Any code path that extracts a user-supplied ZIP archive through ZipArchiver::extract() will write the entire archive to disk without limits. A 42 KB zip bomb can expand to fill available disk space, causing denial of service. On systems where the extraction directory shares a partition with the web root, the entire site becomes unavailable.
Remediation
Apply the same archiveLimits() validation from Installer::unZip() to ZipArchiver::extract():
public function extract($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;
}
}
Affected packages
Start with the recorded fix for your release branch. Check your installed version and test compatibility before upgrading. Fixing this advisory does not rule out other vulnerabilities in the release.
Earlier releases before 2.0.1
Fixed in 2.0.1
335 explicitly affected versions
0.8.0, 0.9.0, 0.9.1, 0.9.10, 0.9.11, 0.9.12, 0.9.13, 0.9.14, 0.9.15, 0.9.16, 0.9.17, 0.9.18, 0.9.19, 0.9.2, 0.9.20, 0.9.21, 0.9.22, 0.9.23, 0.9.24, 0.9.25, 0.9.26, 0.9.27, 0.9.28, 0.9.29, 0.9.3, 0.9.30, 0.9.31, 0.9.32, 0.9.33, 0.9.34, 0.9.35, 0.9.36, 0.9.37, 0.9.38, 0.9.39, 0.9.4, 0.9.40, 0.9.41, 0.9.42, 0.9.43, 0.9.44, 0.9.45, 0.9.5, 0.9.6, 0.9.7, 0.9.8, 0.9.9, 1.0.0, 1.0.0-rc.1, 1.0.0-rc.2, 1.0.0-rc.3, 1.0.0-rc.4, 1.0.0-rc.5, 1.0.0-rc.6, 1.0.1, 1.0.10, 1.0.2, 1.0.3, 1.0.4, 1.0.5, 1.0.6, 1.0.7, 1.0.8, 1.0.9, 1.1.0, 1.1.0-beta.1, 1.1.0-beta.2, 1.1.0-beta.3, 1.1.0-beta.4, 1.1.0-beta.5, 1.1.0-rc.1, 1.1.0-rc.2, 1.1.0-rc.3, 1.1.1, 1.1.10, 1.1.11, 1.1.12, 1.1.13, 1.1.14, 1.1.15, 1.1.16, 1.1.17, 1.1.2, 1.1.3, 1.1.4, 1.1.5, 1.1.6, 1.1.7, 1.1.8, 1.1.9, 1.1.9-rc.1, 1.1.9-rc.2, 1.1.9-rc.3, 1.2.0, 1.2.0-rc.1, 1.2.0-rc.2, 1.2.0-rc.3, 1.2.1, 1.2.2, 1.2.3, 1.2.4, 1.3.0, 1.3.0-rc.1, 1.3.0-rc.2, 1.3.0-rc.3, 1.3.0-rc.4, 1.3.0-rc.5, 1.3.1, 1.3.10, 1.3.2, 1.3.3, 1.3.4, 1.3.5, 1.3.6, 1.3.7, 1.3.8, 1.3.9, 1.4.0, 1.4.0-beta.1, 1.4.0-beta.2, 1.4.0-beta.3, 1.4.0-rc.1, 1.4.0-rc.2, 1.4.1, 1.4.2, 1.4.3, 1.4.4, 1.4.5, 1.4.6, 1.4.7, 1.4.8, 1.5.0, 1.5.0-beta.1, 1.5.0-beta.2, 1.5.0-rc.1, 1.5.1, 1.5.10, 1.5.2, 1.5.3, 1.5.4, 1.5.5, 1.5.6, 1.5.7, 1.5.8, 1.5.9, 1.6.0, 1.6.0-beta.1, 1.6.0-beta.2, 1.6.0-beta.3, 1.6.0-beta.4, 1.6.0-beta.5, 1.6.0-beta.6, 1.6.0-beta.7, 1.6.0-beta.8, 1.6.0-rc.1, 1.6.0-rc.2, 1.6.0-rc.3, 1.6.0-rc.4, 1.6.1, 1.6.10, 1.6.11, 1.6.12, 1.6.13, 1.6.14, 1.6.15, 1.6.16, 1.6.17, 1.6.18, 1.6.19, 1.6.2, 1.6.20, 1.6.21, 1.6.22, 1.6.23, 1.6.24, 1.6.25, 1.6.26, 1.6.27, 1.6.28, 1.6.29, 1.6.3, 1.6.30, 1.6.31, 1.6.4, 1.6.5, 1.6.6, 1.6.7, 1.6.8, 1.6.9, 1.7.0, 1.7.0-beta.1, 1.7.0-beta.10, 1.7.0-beta.2, 1.7.0-beta.3, 1.7.0-beta.4, 1.7.0-beta.5, 1.7.0-beta.6, 1.7.0-beta.7, 1.7.0-beta.8, 1.7.0-beta.9, 1.7.0-rc.1, 1.7.0-rc.10, 1.7.0-rc.11, 1.7.0-rc.12, 1.7.0-rc.13, 1.7.0-rc.14, 1.7.0-rc.15, 1.7.0-rc.16, 1.7.0-rc.17, 1.7.0-rc.18, 1.7.0-rc.19, 1.7.0-rc.2, 1.7.0-rc.20, 1.7.0-rc.3, 1.7.0-rc.4, 1.7.0-rc.5, 1.7.0-rc.6, 1.7.0-rc.7, 1.7.0-rc.8, 1.7.0-rc.9, 1.7.1, 1.7.10, 1.7.12, 1.7.13, 1.7.14, 1.7.15, 1.7.16, 1.7.17, 1.7.18, 1.7.19, 1.7.20, 1.7.21, 1.7.22, 1.7.23, 1.7.24, 1.7.25, 1.7.26, 1.7.26.1, 1.7.27, 1.7.27.1, 1.7.28, 1.7.29, 1.7.29.1, 1.7.3, 1.7.30, 1.7.31, 1.7.32, 1.7.33, 1.7.34, 1.7.35, 1.7.36, 1.7.37, 1.7.37.1, 1.7.38, 1.7.39, 1.7.39.1, 1.7.39.2, 1.7.39.3, 1.7.39.4, 1.7.4, 1.7.40, 1.7.41, 1.7.41.1, 1.7.41.2, 1.7.42, 1.7.42.1, 1.7.42.2, 1.7.42.3, 1.7.43, 1.7.44, 1.7.45, 1.7.46, 1.7.47, 1.7.48, 1.7.49, 1.7.49.1, 1.7.49.2, 1.7.49.3, 1.7.49.4, 1.7.49.5, 1.7.5, 1.7.51, 1.7.52, 1.7.53, 1.7.53.1, 1.7.53.2, 1.7.53.3, 1.7.6, 1.7.7, 1.7.8, 1.7.9, 1.8.0-beta.1, 1.8.0-beta.10, 1.8.0-beta.11, 1.8.0-beta.12, 1.8.0-beta.13, 1.8.0-beta.14, 1.8.0-beta.15, 1.8.0-beta.16, 1.8.0-beta.17, 1.8.0-beta.18, 1.8.0-beta.19, 1.8.0-beta.2, 1.8.0-beta.20, 1.8.0-beta.21, 1.8.0-beta.22, 1.8.0-beta.23, 1.8.0-beta.24, 1.8.0-beta.25, 1.8.0-beta.26, 1.8.0-beta.27, 1.8.0-beta.28, 1.8.0-beta.29, 1.8.0-beta.3, 1.8.0-beta.4, 1.8.0-beta.5, 1.8.0-beta.6, 1.8.0-beta.7, 1.8.0-beta.8, 1.8.0-beta.9, 2.0.0, 2.0.0-beta.1, 2.0.0-beta.2, 2.0.0-beta.3, 2.0.0-beta.4, 2.0.0-rc.1, 2.0.0-rc.10, 2.0.0-rc.2, 2.0.0-rc.3, 2.0.0-rc.4, 2.0.0-rc.5, 2.0.0-rc.6, 2.0.0-rc.7, 2.0.0-rc.8, 2.0.0-rc.9
View affected-version evidence
{
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.0.1"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.8.0",
"0.9.0",
"0.9.1",
"0.9.10",
"0.9.11",
"0.9.12",
"0.9.13",
"0.9.14",
"0.9.15",
"0.9.16",
"0.9.17",
"0.9.18",
"0.9.19",
"0.9.2",
"0.9.20",
"0.9.21",
"0.9.22",
"0.9.23",
"0.9.24",
"0.9.25",
"0.9.26",
"0.9.27",
"0.9.28",
"0.9.29",
"0.9.3",
"0.9.30",
"0.9.31",
"0.9.32",
"0.9.33",
"0.9.34",
"0.9.35",
"0.9.36",
"0.9.37",
"0.9.38",
"0.9.39",
"0.9.4",
"0.9.40",
"0.9.41",
"0.9.42",
"0.9.43",
"0.9.44",
"0.9.45",
"0.9.5",
"0.9.6",
"0.9.7",
"0.9.8",
"0.9.9",
"1.0.0",
"1.0.0-rc.1",
"1.0.0-rc.2",
"1.0.0-rc.3",
"1.0.0-rc.4",
"1.0.0-rc.5",
"1.0.0-rc.6",
"1.0.1",
"1.0.10",
"1.0.2",
"1.0.3",
"1.0.4",
"1.0.5",
"1.0.6",
"1.0.7",
"1.0.8",
"1.0.9",
"1.1.0",
"1.1.0-beta.1",
"1.1.0-beta.2",
"1.1.0-beta.3",
"1.1.0-beta.4",
"1.1.0-beta.5",
"1.1.0-rc.1",
"1.1.0-rc.2",
"1.1.0-rc.3",
"1.1.1",
"1.1.10",
"1.1.11",
"1.1.12",
"1.1.13",
"1.1.14",
"1.1.15",
"1.1.16",
"1.1.17",
"1.1.2",
"1.1.3",
"1.1.4",
"1.1.5",
"1.1.6",
"1.1.7",
"1.1.8",
"1.1.9",
"1.1.9-rc.1",
"1.1.9-rc.2",
"1.1.9-rc.3",
"1.2.0",
"1.2.0-rc.1",
"1.2.0-rc.2",
"1.2.0-rc.3",
"1.2.1",
"1.2.2",
"1.2.3",
"1.2.4",
"1.3.0",
"1.3.0-rc.1",
"1.3.0-rc.2",
"1.3.0-rc.3",
"1.3.0-rc.4",
"1.3.0-rc.5",
"1.3.1",
"1.3.10",
"1.3.2",
"1.3.3",
"1.3.4",
"1.3.5",
"1.3.6",
"1.3.7",
"1.3.8",
"1.3.9",
"1.4.0",
"1.4.0-beta.1",
"1.4.0-beta.2",
"1.4.0-beta.3",
"1.4.0-rc.1",
"1.4.0-rc.2",
"1.4.1",
"1.4.2",
"1.4.3",
"1.4.4",
"1.4.5",
"1.4.6",
"1.4.7",
"1.4.8",
"1.5.0",
"1.5.0-beta.1",
"1.5.0-beta.2",
"1.5.0-rc.1",
"1.5.1",
"1.5.10",
"1.5.2",
"1.5.3",
"1.5.4",
"1.5.5",
"1.5.6",
"1.5.7",
"1.5.8",
"1.5.9",
"1.6.0",
"1.6.0-beta.1",
"1.6.0-beta.2",
"1.6.0-beta.3",
"1.6.0-beta.4",
"1.6.0-beta.5",
"1.6.0-beta.6",
"1.6.0-beta.7",
"1.6.0-beta.8",
"1.6.0-rc.1",
"1.6.0-rc.2",
"1.6.0-rc.3",
"1.6.0-rc.4",
"1.6.1",
"1.6.10",
"1.6.11",
"1.6.12",
"1.6.13",
"1.6.14",
"1.6.15",
"1.6.16",
"1.6.17",
"1.6.18",
"1.6.19",
"1.6.2",
"1.6.20",
"1.6.21",
"1.6.22",
"1.6.23",
"1.6.24",
"1.6.25",
"1.6.26",
"1.6.27",
"1.6.28",
"1.6.29",
"1.6.3",
"1.6.30",
"1.6.31",
"1.6.4",
"1.6.5",
"1.6.6",
"1.6.7",
"1.6.8",
"1.6.9",
"1.7.0",
"1.7.0-beta.1",
"1.7.0-beta.10",
"1.7.0-beta.2",
"1.7.0-beta.3",
"1.7.0-beta.4",
"1.7.0-beta.5",
"1.7.0-beta.6",
"1.7.0-beta.7",
"1.7.0-beta.8",
"1.7.0-beta.9",
"1.7.0-rc.1",
"1.7.0-rc.10",
"1.7.0-rc.11",
"1.7.0-rc.12",
"1.7.0-rc.13",
"1.7.0-rc.14",
"1.7.0-rc.15",
"1.7.0-rc.16",
"1.7.0-rc.17",
"1.7.0-rc.18",
"1.7.0-rc.19",
"1.7.0-rc.2",
"1.7.0-rc.20",
"1.7.0-rc.3",
"1.7.0-rc.4",
"1.7.0-rc.5",
"1.7.0-rc.6",
"1.7.0-rc.7",
"1.7.0-rc.8",
"1.7.0-rc.9",
"1.7.1",
"1.7.10",
"1.7.12",
"1.7.13",
"1.7.14",
"1.7.15",
"1.7.16",
"1.7.17",
"1.7.18",
"1.7.19",
"1.7.20",
"1.7.21",
"1.7.22",
"1.7.23",
"1.7.24",
"1.7.25",
"1.7.26",
"1.7.26.1",
"1.7.27",
"1.7.27.1",
"1.7.28",
"1.7.29",
"1.7.29.1",
"1.7.3",
"1.7.30",
"1.7.31",
"1.7.32",
"1.7.33",
"1.7.34",
"1.7.35",
"1.7.36",
"1.7.37",
"1.7.37.1",
"1.7.38",
"1.7.39",
"1.7.39.1",
"1.7.39.2",
"1.7.39.3",
"1.7.39.4",
"1.7.4",
"1.7.40",
"1.7.41",
"1.7.41.1",
"1.7.41.2",
"1.7.42",
"1.7.42.1",
"1.7.42.2",
"1.7.42.3",
"1.7.43",
"1.7.44",
"1.7.45",
"1.7.46",
"1.7.47",
"1.7.48",
"1.7.49",
"1.7.49.1",
"1.7.49.2",
"1.7.49.3",
"1.7.49.4",
"1.7.49.5",
"1.7.5",
"1.7.51",
"1.7.52",
"1.7.53",
"1.7.53.1",
"1.7.53.2",
"1.7.53.3",
"1.7.6",
"1.7.7",
"1.7.8",
"1.7.9",
"1.8.0-beta.1",
"1.8.0-beta.10",
"1.8.0-beta.11",
"1.8.0-beta.12",
"1.8.0-beta.13",
"1.8.0-beta.14",
"1.8.0-beta.15",
"1.8.0-beta.16",
"1.8.0-beta.17",
"1.8.0-beta.18",
"1.8.0-beta.19",
"1.8.0-beta.2",
"1.8.0-beta.20",
"1.8.0-beta.21",
"1.8.0-beta.22",
"1.8.0-beta.23",
"1.8.0-beta.24",
"1.8.0-beta.25",
"1.8.0-beta.26",
"1.8.0-beta.27",
"1.8.0-beta.28",
"1.8.0-beta.29",
"1.8.0-beta.3",
"1.8.0-beta.4",
"1.8.0-beta.5",
"1.8.0-beta.6",
"1.8.0-beta.7",
"1.8.0-beta.8",
"1.8.0-beta.9",
"2.0.0",
"2.0.0-beta.1",
"2.0.0-beta.2",
"2.0.0-beta.3",
"2.0.0-beta.4",
"2.0.0-rc.1",
"2.0.0-rc.10",
"2.0.0-rc.2",
"2.0.0-rc.3",
"2.0.0-rc.4",
"2.0.0-rc.5",
"2.0.0-rc.6",
"2.0.0-rc.7",
"2.0.0-rc.8",
"2.0.0-rc.9"
]
}