CVE-2026-2789 in Firefox
Summary
by MITRE • 02/24/2026
Use-after-free in the Graphics: ImageLib component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.
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Analysis
by VulDB Data Team • 03/04/2026
This vulnerability represents a critical use-after-free condition within the Graphics: ImageLib component of Mozilla's Firefox and Thunderbird email clients. The flaw occurs when the application attempts to access memory that has already been freed, creating a potential exploitation vector for remote code execution. The vulnerability affects multiple product versions including Firefox versions prior to 148, Firefox ESR versions prior to 115.33 and 140.8, and Thunderbird versions prior to 148 and 140.8, indicating a widespread impact across the Mozilla ecosystem. The root cause lies in improper memory management within the image processing subsystem where freed memory blocks are still referenced during subsequent operations.
The technical implementation of this vulnerability stems from inadequate null pointer checks and memory lifecycle management within the Graphics: ImageLib component. When processing certain image formats, the system allocates memory for image data structures, processes the content, and subsequently frees the memory. However, under specific conditions involving malformed image data or particular processing sequences, the application continues to reference these freed memory locations. This behavior creates a classic use-after-free scenario that can be exploited by attackers who craft malicious image files designed to trigger the vulnerable code path. The flaw aligns with CWE-416, which specifically addresses use-after-free vulnerabilities in memory management operations.
The operational impact of this vulnerability extends beyond simple application instability, presenting significant security risks to end users. Remote attackers can potentially execute arbitrary code on affected systems by delivering malicious image content through web pages, email attachments, or other media formats processed by the vulnerable applications. The exploitability of this vulnerability is heightened by the fact that it operates within the core image processing functionality that is frequently accessed during normal browsing and email operations. Attackers can leverage this weakness to gain unauthorized access to systems, escalate privileges, or establish persistent backdoors, making it particularly dangerous in enterprise environments where these applications are widely deployed.
Organizations should prioritize immediate patching of all affected versions to mitigate the risk of exploitation. The recommended mitigation strategy involves upgrading to the latest supported versions of Firefox and Thunderbird, specifically Firefox 148 and later, Firefox ESR 115.33 and 140.8 and later, and Thunderbird 148 and 140.8 and later. Security administrators should also implement network-based controls such as content filtering and sandboxing measures to limit exposure while patches are deployed. Additional protective measures include disabling automatic image loading in email clients, implementing strict file type validation for image content, and monitoring for suspicious network activity that might indicate exploitation attempts. The vulnerability's classification under the ATT&CK framework would fall under T1059.007 for remote code execution techniques, with potential lateral movement capabilities once initial compromise occurs.