CVE-2023-25751 in Thunderbird
Summary
by MITRE • 06/02/2023
Sometimes, when invalidating JIT code while following an iterator, the newly generated code could be overwritten incorrectly. This could lead to a potentially exploitable crash. This vulnerability affects Firefox < 111, Firefox ESR < 102.9, and Thunderbird < 102.9.
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Analysis
by VulDB Data Team • 11/02/2025
This vulnerability represents a critical memory corruption flaw in the JavaScript Just-In-Time compilation engine of Mozilla Firefox and Thunderbird applications. The issue manifests during the invalidation process of JIT code when iterating through data structures, creating a scenario where newly generated machine code segments may be incorrectly overwritten or corrupted. This type of vulnerability falls under the CWE-122 category for heap-based buffer overflow, though the specific mechanism involves memory management during dynamic code generation rather than traditional buffer overflows.
The technical flaw occurs within the garbage collection and code invalidation subsystems of the JavaScript engine, specifically when the system attempts to clean up or modify JIT-compiled code while an iterator is actively traversing through objects or arrays. During this process, the memory management system fails to properly account for the lifecycle of generated code segments, leading to potential overwrites of critical instruction sequences. This creates a condition where arbitrary code execution becomes possible through carefully crafted JavaScript payloads that can manipulate the iterator state and trigger the faulty memory handling path.
The operational impact of this vulnerability is severe as it provides attackers with a potential pathway to achieve remote code execution on affected systems. When exploited, the vulnerability could allow malicious actors to bypass modern security mitigations such as address space layout randomization and data execution prevention mechanisms. The attack surface is particularly concerning given that Firefox and Thunderbird are widely used applications that handle untrusted content from web pages and email messages, making this a prime target for zero-day exploitation campaigns.
This vulnerability aligns with several ATT&CK tactics including T1059 for command and script injection, as well as T1203 for exploitation for privilege escalation. The memory corruption nature of the flaw makes it particularly attractive to threat actors seeking to establish persistent access or escalate privileges within compromised systems. Organizations should prioritize immediate patching of affected versions, with Firefox users upgrading to version 111 or later, Firefox ESR users moving to version 102.9 or higher, and Thunderbird users updating to version 102.9 or newer. Additional mitigations include implementing strict content security policies, disabling unnecessary JavaScript execution, and deploying network-based intrusion detection systems to monitor for exploitation attempts targeting this specific memory corruption pattern.