CVE-2024-38312 Overview
CVE-2024-38312 affects Firefox for iOS versions earlier than 127. The vulnerability causes private browsing data to persist incorrectly inside the sandboxed app bundle after the app terminates. Location history and webpage thumbnails from private tabs can remain on the device instead of being cleared. This behavior contradicts the expected privacy guarantees of Private Browsing Mode and exposes sensitive user activity to anyone with local file access or subsequent app inspection. The issue is classified under [CWE-922: Insecure Storage of Sensitive Information].
Critical Impact
Private browsing artifacts including location data and page thumbnails remain accessible in the app sandbox after termination, undermining private tab confidentiality on iOS devices running Firefox before version 127.
Affected Products
- Mozilla Firefox for iOS versions prior to 127
- iOS builds of Firefox distributed through the Apple App Store
- Firefox Mobile installations that use Private Browsing Mode on iPhone and iPad
Discovery Timeline
- 2024-06-13 - CVE-2024-38312 published to the National Vulnerability Database
- 2024-06-13 - Mozilla publishes advisory MFSA-2024-27
- 2026-08-19 - Last updated in NVD database
Technical Details for CVE-2024-38312
Vulnerability Analysis
The vulnerability is a mobile insecure data storage flaw in Firefox for iOS. When a user browses in private tabs, the browser generates supporting artifacts such as location history entries and webpage thumbnail images. These artifacts should be discarded when the app is terminated to maintain the confidentiality expectations of Private Browsing Mode.
Instead, the affected versions write some of this data to locations inside the app's sandbox that survive termination. A subsequent launch of the app, or forensic inspection of the device backup, can reveal thumbnails and location metadata associated with private sessions. Exploitation requires user interaction, since the victim must browse in private tabs before the residual data can be observed.
Root Cause
The root cause is improper lifecycle management of private session data within the iOS sandbox. Cleanup routines that run on tab close or app exit do not fully remove all artifacts written during private browsing. Files persist inside directories that iOS preserves across app terminations, so the data outlives the browsing session it belongs to.
Attack Vector
An attacker needs read access to the Firefox app sandbox to retrieve the residual data. This access can be obtained through a device backup, a paired computer, forensic tooling on an unlocked device, or a companion app vulnerability that grants sandbox visibility. The vulnerability does not enable remote code execution, but it violates the integrity of the private browsing privacy contract for stored artifacts.
No public proof-of-concept or exploit code is available for CVE-2024-38312. See Mozilla Bug Report #1878578 for developer discussion of the fix.
Detection Methods for CVE-2024-38312
Indicators of Compromise
- Presence of thumbnail image files or location history records inside the Firefox iOS app sandbox after private tabs have been closed and the app terminated.
- Firefox for iOS build version reported as less than 127 on managed devices.
- Backup artifacts extracted from iTunes or Finder backups that contain private-tab-derived thumbnails or geolocation entries.
Detection Strategies
- Inventory iOS endpoints through Mobile Device Management to identify Firefox installations running versions earlier than 127.
- Review device backup contents during forensic reviews for residual Firefox private session data.
- Correlate Firefox version telemetry with app usage patterns to prioritize devices where private browsing is heavily used.
Monitoring Recommendations
- Enforce MDM policies that report browser versions on corporate iOS devices and flag outdated Firefox builds.
- Monitor App Store update compliance to confirm Firefox for iOS is upgraded to 127 or later.
- Audit backup and sync workflows that may propagate residual private browsing data to shared storage.
How to Mitigate CVE-2024-38312
Immediate Actions Required
- Update Firefox for iOS to version 127 or later through the Apple App Store on every affected device.
- Manually clear existing Firefox website data and history on devices that previously used Private Browsing Mode before the upgrade.
- Rotate or review any credentials or location-sensitive services accessed through private tabs on unpatched devices.
Patch Information
Mozilla addressed the issue in Firefox for iOS 127. Details are documented in Mozilla Security Advisory MFSA-2024-27 and the tracking record at Mozilla Bug Report #1878578. Users should install the update from the App Store rather than relying on side-channel distributions.
Workarounds
- Avoid using Firefox Private Browsing Mode on iOS until the app is updated to version 127 or later.
- Use an alternative browser with verified private browsing behavior for sensitive sessions during the update window.
- Delete the Firefox app and reinstall a patched version to guarantee removal of legacy private browsing artifacts from the sandbox.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
