CVE-2025-1017 in Thunderbird
Summary
by MITRE • 02/04/2025
Memory safety bugs present in Firefox 134, Thunderbird 134, Firefox ESR 128.6, and Thunderbird 128.6. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 135, Firefox ESR 128.7, Thunderbird 128.7, and Thunderbird 135.
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Analysis
by VulDB Data Team • 04/15/2026
This vulnerability represents a critical memory safety issue affecting multiple Mozilla products including Firefox and Thunderbird across both current and extended support release channels. The identified memory safety bugs demonstrate the inherent complexity of modern web browsers which must process vast amounts of untrusted data while maintaining robust memory management. These vulnerabilities were discovered during routine security audits and represent a concerning trend of memory corruption flaws that could potentially be weaponized by malicious actors. The presence of evidence indicating memory corruption suggests that attackers could exploit these weaknesses to gain unauthorized control over affected systems.
The technical flaw manifests as memory safety violations that occur during normal browser operations when processing web content or email data. Memory corruption vulnerabilities typically arise from improper handling of memory allocation, deallocation, or access patterns within the browser's rendering engine or mail processing components. These issues are particularly dangerous because they can lead to arbitrary code execution when exploited, allowing attackers to bypass security controls and potentially escalate privileges. The bugs are categorized under memory safety issues that align with common weakness enumerations such as CWE-125 out-of-bounds read conditions and CWE-787 out-of-bounds write conditions that are frequently exploited in browser-based attacks.
The operational impact of these vulnerabilities extends beyond individual user devices to potentially compromise entire organizational networks. When exploited, these memory safety bugs could enable attackers to execute malicious code on targeted systems, potentially leading to data breaches, system compromise, or lateral movement within networks. The vulnerability affects both desktop and mobile versions of the affected products, making it particularly concerning for organizations that rely on these applications for email and web browsing. The fact that these vulnerabilities were present in both current and extended support releases indicates a persistent issue that required immediate attention across multiple product lines.
Organizations should prioritize immediate deployment of the available security patches for Firefox 135, Firefox ESR 128.7, Thunderbird 128.7, and Thunderbird 135 to mitigate the risk of exploitation. The ATT&CK framework categorizes such vulnerabilities under technique T1059 command and scripting interpreter for execution, as attackers would leverage these memory corruption flaws to establish persistent access through arbitrary code execution. Security teams should also implement network monitoring to detect potential exploitation attempts and consider deploying additional security controls such as exploit prevention software and web application firewalls. Regular security assessments and vulnerability management processes should be enhanced to identify similar issues in other browser components and third-party libraries that may present similar memory safety risks. The vulnerability highlights the importance of maintaining up-to-date security patches and demonstrates how memory safety issues in complex software systems can create significant attack surface vulnerabilities.