CVE-2025-4093 in Thunderbird ESR
Summary
by MITRE • 04/29/2025
Memory safety bug present in Firefox ESR 128.9, and Thunderbird 128.9. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability affects Firefox ESR < 128.10 and Thunderbird ESR < 128.10.
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Analysis
by VulDB Data Team • 08/16/2025
This memory safety vulnerability identified as CVE-2025-4093 represents a critical concern within Mozilla's Firefox ESR 128.9 and Thunderbird 128.9 product lines. The flaw manifests as a memory corruption issue that demonstrates characteristics consistent with memory safety bugs commonly classified under CWE-787, which encompasses out-of-bounds writes and other memory corruption vulnerabilities. Such vulnerabilities typically arise from insufficient bounds checking in memory allocation and deallocation operations, creating opportunities for attackers to manipulate program execution flow through crafted inputs that trigger buffer overflows or use-after-free conditions. The presence of memory corruption patterns indicates that the vulnerability likely exists within the browser's rendering engine or mail client's message processing components where complex data structures are manipulated. The fact that this vulnerability affects both Firefox ESR and Thunderbird ESR platforms suggests it may originate from shared codebases or common libraries used in both applications, potentially including components related to HTML parsing, JavaScript execution, or message handling functions. Security researchers have identified that exploitation of this vulnerability could potentially lead to arbitrary code execution, making it a high-severity concern for organizations relying on these email and web browsing platforms. The vulnerability's impact extends beyond individual user compromise to encompass potential enterprise-wide security risks, particularly in environments where these applications are extensively used for business communications and web access. Organizations should recognize that this vulnerability aligns with ATT&CK technique T1059.007, which covers scripting through command-line interfaces, as exploitation could potentially involve malicious scripts or payloads delivered through compromised email messages or web content. The specific version constraints indicate that Firefox ESR versions prior to 128.10 and Thunderbird ESR versions prior to 128.10 remain vulnerable, while patched releases have addressed the underlying memory safety issues. This vulnerability type often requires sophisticated exploitation techniques that leverage multiple attack vectors to achieve successful compromise, potentially involving heap spraying, return-oriented programming, or other advanced exploitation methods. The memory corruption characteristics suggest that attackers might be able to manipulate memory layout through carefully crafted inputs, potentially leading to privilege escalation or complete system compromise depending on the execution context. Organizations should prioritize immediate patch deployment to address this vulnerability, as the potential for remote code execution makes it a critical security concern that could be actively exploited in the wild. The vulnerability's classification as a memory safety bug places it within the broader category of software reliability issues that can undermine the fundamental security posture of web browsers and email clients, emphasizing the importance of robust memory management practices in security-critical applications. The remediation strategy should include not only patching affected systems but also implementing network monitoring to detect potential exploitation attempts and establishing incident response procedures for rapid containment if compromise occurs.