CVE-2022-1097: Mozilla Firefox Use-After-Free Vulnerability

CVE-2022-1097 Overview

CVE-2022-1097 is a use-after-free vulnerability affecting Mozilla Firefox, Firefox ESR, and Thunderbird. The flaw exists in how NSSToken objects are referenced via direct pointers, which could be accessed in an unsafe way across different threads. This race condition can lead to a use-after-free scenario, resulting in a potentially exploitable crash.

Critical Impact

Successful exploitation of this vulnerability could allow an attacker to cause application crashes and potentially achieve arbitrary code execution through memory corruption.

Affected Products

• Mozilla Firefox versions prior to 99
• Mozilla Firefox ESR versions prior to 91.8
• Mozilla Thunderbird versions prior to 91.8

Discovery Timeline

• 2022-12-22 - CVE-2022-1097 published to NVD
• 2025-04-16 - Last updated in NVD database

Technical Details for CVE-2022-1097

Vulnerability Analysis

This vulnerability is classified as CWE-416 (Use After Free), a memory corruption flaw that occurs when a program continues to use a pointer after the memory it references has been freed. In this case, the issue stems from Mozilla's Network Security Services (NSS) library, specifically in the handling of NSSToken objects.

The vulnerability arises from improper synchronization when accessing NSSToken objects across multiple threads. When one thread frees an NSSToken object while another thread still holds a direct pointer to it, subsequent access attempts by the second thread result in accessing freed memory. This can lead to unpredictable behavior including crashes or potentially arbitrary code execution if an attacker can control the contents of the freed memory region.

The attack requires user interaction, as the victim must visit a malicious website or open a crafted email that triggers the vulnerable code path. While the primary demonstrated impact is denial of service through application crashes, the nature of use-after-free vulnerabilities means that code execution may be achievable with sufficient exploitation effort.

Root Cause

The root cause of CVE-2022-1097 lies in the use of direct pointers to reference NSSToken objects without proper thread synchronization mechanisms. The NSS library failed to implement adequate locking or reference counting when NSSToken objects were accessed from multiple threads concurrently. This design flaw allows for a race condition where memory can be freed by one thread while still being referenced by another.

Attack Vector

The attack vector for this vulnerability is network-based and requires user interaction. An attacker would need to craft malicious web content that triggers the race condition in the NSSToken handling code. This could be achieved through:

1. A malicious website that performs cryptographic operations designed to trigger concurrent access to NSSToken objects
2. A crafted email with embedded content that exploits the vulnerability when processed by Thunderbird
3. Content that manipulates the timing of NSS operations to increase the likelihood of the race condition occurring

The vulnerability exploits the inherent unpredictability of thread scheduling to create a window where freed memory is accessed. While achieving reliable exploitation can be challenging due to the timing-dependent nature of race conditions, sophisticated attackers may be able to increase the probability of success through heap manipulation techniques.

Detection Methods for CVE-2022-1097

Indicators of Compromise

• Unexpected crashes of Firefox, Firefox ESR, or Thunderbird applications with crash reports referencing NSS or NSSToken components
• Memory access violation errors in application logs indicating use-after-free conditions
• Unusual browser behavior when visiting specific websites that may be attempting exploitation

Detection Strategies

• Monitor for application crashes with signatures matching memory corruption in NSS library components
• Deploy endpoint detection solutions capable of identifying heap spray or memory manipulation techniques commonly used in use-after-free exploitation
• Implement browser telemetry analysis to detect patterns of repeated crashes that may indicate exploitation attempts

Monitoring Recommendations

• Enable crash reporting in Mozilla applications to capture detailed information about memory corruption events
• Configure security monitoring tools to alert on repeated application restarts that may indicate exploitation attempts
• Review network traffic for connections to known malicious domains that may be hosting exploit code

How to Mitigate CVE-2022-1097

Immediate Actions Required

• Update Mozilla Firefox to version 99 or later immediately
• Update Mozilla Firefox ESR to version 91.8 or later
• Update Mozilla Thunderbird to version 91.8 or later
• Verify that automatic updates are enabled for all Mozilla products in your environment

Patch Information

Mozilla has released security patches addressing this vulnerability in the following versions:

• Firefox 99 - Contains the fix for this vulnerability (MFSA 2022-13)
• Firefox ESR 91.8 - Extended Support Release with the security fix (MFSA 2022-14)
• Thunderbird 91.8 - Email client with the vulnerability patched (MFSA 2022-15)

The technical details of the fix can be found in Mozilla Bug Report #1745667.

Workarounds

• If immediate patching is not possible, consider restricting access to untrusted websites through web filtering solutions
• Disable JavaScript execution for untrusted content as a temporary measure to reduce attack surface
• Consider using alternative browsers for critical tasks until patching can be completed