MobSF Framework Zero-Day Vulnerability Allows Attackers to Trigger DoS in Scan Results

A recently discovered zero-day vulnerability in the Mobile Security Framework (MobSF) has raised alarms in the cybersecurity community.

The vulnerability, which allows attackers to cause a partial Denial of Service (DoS) on scan results and the iOS Dynamic Analyzer functionality, was disclosed on GitHub yesterday by Ajin Abraham, under the advisory GHSA-jrm8-xgf3-fwqr.

Technical Overview

The vulnerability, classified under CWE-1287: Improper Validation of Specified Type of Input, resides in MobSF version 4.2.9.

A flaw in the URL regex parsing in the urls.py file allows attackers to exploit improperly formatted bundle ID values and disrupt the functionality of the platform. Specifically, the issue occurs in the following code snippet:

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

re_path(fr'^ios/view_report/{bundle_id_regex}', ios_view_report, name='ios_view_report')

Exploitation and Impact

The vulnerability can be triggered by uploading a malicious IPA file where the <key>CFBundleIdentifier</key> value in the Info.plist file has been intentionally modified to include restricted characters not allowed under Apple’s guidelines.

When MobSF attempts to parse this invalid bundle ID, it throws a 500 server error, rendering scan results and analyzer pages unavailable until the malicious file is manually removed. The affected endpoints include:

• /recent_scans/
• /ios/dynamic_analysis/

This flaw has been rated as a moderate severity issue with the following CVSS scores:

• CVSS v4.0: 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 v3.1: 6.5 (AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H)

Reproduction Steps

1. Unzip an IPA file of any iOS application.
2. Modify the <key>CFBundleIdentifier</key> in the Info.plist file by adding restricted characters (e.g., ‘).
3. Repack the IPA file and upload it to MobSF’s static analysis feature.
4. Access the impacted pages, which will return a 500 error, confirming the DoS.

To address this issue, MobSF has released a patched version, 4.3.1 in Gihub, which includes stricter validations for bundle IDs.

Administrators are advised to upgrade immediately to the latest version to prevent exploitation. For temporary mitigation, ensure that uploaded bundle IDs are validated against the defined regex: r'(?P<bundle_id>([a-zA-Z0-9]{1}[\w.-]{1,255}))$ and manually review uploads for suspicious characters.

The vulnerability was discovered by Oleg Surnin from Positive Technologies. His detailed analysis highlighted the risks of improper input validation and underscored the necessity of adhering to Apple’s strict bundle ID documentation.

This vulnerability serves as a reminder of the critical need for robust input validation in software development, particularly in security-related frameworks like MobSF.

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