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A critical vulnerability, tracked as CVE-2025-13016, was discovered in the WebAssembly engine's JavaScript component of Mozilla Firefox and Thunderbird, exposing over 180 million users to the risk of arbitrary code execution. The flaw, introduced in April 2025, results from incorrect boundary conditions in pointer arithmetic within the garbage collection process, leading to a stack buffer overflow. Attackers can exploit this vulnerability by luring users to malicious websites or sending crafted email content, potentially gaining complete control over the affected browser or mail client process. The vulnerability affects Firefox versions below 145 and Thunderbird versions prior to 145, including their respective ESR releases.
Mozilla responded promptly by releasing security patches in Firefox 145, Firefox ESR 140.5, Thunderbird 145, and Thunderbird ESR 140.5. Security experts and vendors have emphasized the importance of immediate updates to mitigate the risk, as the flaw remained undetected for six months and could have compromised sensitive user data. Organizations and individuals are strongly advised to deploy the latest updates to ensure protection against potential exploitation of this high-severity vulnerability.
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4 events from the most recent confirmed update back to the earliest known activity.
Security media publicly disclosed details of CVE-2025-13016, describing the arbitrary code execution risk from malicious webpages and the potential exposure of millions of Firefox users. Reports noted the bug had gone undetected for roughly six months before disclosure.
Mozilla released patched versions addressing CVE-2025-13016, including Firefox 145, Firefox ESR 140.5, Thunderbird 145, and Thunderbird ESR 140.5. Users and defenders were urged to update promptly to reduce exploitation risk.
AI security firm AISLE reportedly discovered CVE-2025-13016, a high-severity stack buffer overflow in Mozilla's WebAssembly engine that could enable arbitrary code execution. The issue affected Firefox and, according to reporting, Thunderbird as well when triggered through malicious content and user interaction.
The flaw later tracked as CVE-2025-13016 was reportedly introduced into Firefox in April 2025 in template-heavy WebAssembly garbage-collection code. The bug involved incorrect boundary checks and faulty pointer arithmetic that could lead to a stack buffer overflow.
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Mozilla disclosed and patched two high-severity vulnerability groups, **`CVE-2026-5731`** and **`CVE-2026-6786`**, affecting multiple Firefox and Thunderbird release lines. The flaws were described as memory safety bugs with evidence of memory corruption that could potentially be exploited for **arbitrary code execution**. Affected versions included Firefox earlier than **149.0.2** and **150**, Firefox ESR earlier than **115.34.1**, **140.9.1**, and **140.10**, plus corresponding Thunderbird and Thunderbird ESR releases. The fixes were shipped across standard and ESR channels in **Firefox 149.0.2**, **Firefox 150**, **Firefox ESR 115.34.1**, **Firefox ESR 140.9.1**, **Firefox ESR 140.10**, **Thunderbird 149.0.2**, **Thunderbird 150**, and **Thunderbird ESR 140.9.1/140.10**. The CVE records link the issues to memory-corruption weaknesses including **`CWE-119`**, **`CWE-125`**, **`CWE-787`**, and **`CWE-416`**, and assign high-impact CVSS vectors reflecting potential compromise of confidentiality, integrity, and availability if exploited.
Jun 29, 2026
Multiple critical vulnerabilities were identified in Mozilla Firefox and Firefox ESR, with the most severe enabling arbitrary code execution. Affected versions include Firefox prior to 146, Firefox ESR prior to 115.31, and Firefox ESR prior to 140.6. The vulnerabilities include use-after-free in WebRTC (`CVE-2025-14321`), sandbox escape in Graphics (`CVE-2025-14322`), privilege escalation in the DOM (`CVE-2025-14323`), JIT miscompilation in the JavaScript Engine (`CVE-2025-14324`, `CVE-2025-14325`), and multiple memory safety bugs. Exploitation could allow attackers to install programs, modify or delete data, or create new accounts with full user rights, depending on the privileges of the compromised user. There are currently no reports of these vulnerabilities being exploited in the wild. Security advisories from both the Canadian Centre for Cyber Security and the Multi-State Information Sharing and Analysis Center (MS-ISAC) urge users and administrators to apply the latest updates immediately to mitigate risk. The advisories highlight the importance of prompt patching, especially for large organizations and government entities, as the risk is assessed as high for these sectors. The updates address all known vulnerabilities, and users with fewer system privileges are less impacted than those with administrative rights.
Jun 29, 2026
Mozilla released security updates for **Firefox 154**, supported **Firefox ESR** branches, and **Thunderbird** to fix a broad set of vulnerabilities affecting desktop and mobile users. Government and vendor advisories said the updates address **3 critical** and **17 high-severity** flaws involving arbitrary code execution, privilege escalation, security restriction bypass, sandbox escape, site isolation failures, use-after-free conditions, and information disclosure. Firefox 154 also introduced product changes including expanded Local Access Network protections for WebSocket connections, while security notices from Canada and Italy urged organizations to review Mozilla bulletins and update affected installations. Tenable and downstream Linux advisories flagged the issue set as **critical** across Windows, macOS, and Slackware packages, with affected versions including Firefox releases prior to 154, multiple ESR builds before their patched versions, and Thunderbird releases prior to **140.14** or **154.0** depending on branch. Nessus coverage tied the fixes to numerous CVEs, including **`CVE-2026-74990`** as a scoring reference in several advisories, and highlighted specific Thunderbird issues such as a Remote Settings Client sandbox escape, a CanvasWebGL site isolation flaw, a DOM: Networking privilege escalation bug, and WebAssembly and garbage-collection use-after-free vulnerabilities. The recommended action across all notices was to upgrade Mozilla products to the latest patched versions immediately.
Aug 26, 2026