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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.
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4 events from the most recent confirmed update back to the earliest known activity.
The CVE-2026-6786 record was created and populated with a description, Bugzilla and Mozilla advisory references, a CVSS v3.1 vector, and CWE classifications including CWE-125, CWE-787, and CWE-416.
Mozilla fixed memory safety bugs tracked as CVE-2026-6786 in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird ESR 140.10. The affected versions included Firefox 149 and ESR 140.9, and Mozilla noted some bugs showed evidence of memory corruption with possible arbitrary code execution impact.
The CVE-2026-5731 entry was updated to add a CVSS v3.1 vector, CWE-119 classification, and links to Mozilla advisory and Bugzilla references documenting the issue and fixes.
Mozilla addressed memory safety bugs tracked as CVE-2026-5731 in Firefox 149.0.2, Firefox ESR 115.34.1 and 140.9.1, and Thunderbird 149.0.2 and ESR 140.9.1. Mozilla said some bugs showed evidence of memory corruption and could potentially be exploited for arbitrary code execution with sufficient effort.
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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
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.
Jun 29, 2026
Mozilla released **Firefox 150** and updated **Firefox ESR** branches to address multiple security vulnerabilities, prompting downstream advisories from Debian and the Canadian Centre for Cyber Security. The fixes cover Firefox versions prior to `150`, Firefox ESR versions prior to `140.10` and `115.35`, and include vulnerabilities tracked as **CVE-2026-6768**, **CVE-2026-6784**, **CVE-2026-6785**, and **CVE-2026-6786**. **CVE-2026-6768** was described as a mitigation bypass in Firefox’s `Networking: Cookies` component and was assigned a **CVSS 9.8** score, indicating potentially severe impact if left unpatched. Mozilla also shipped related security fixes in **Thunderbird 150**, which uses Firefox’s web engine and addressed issues including a clickjacking and information disclosure flaw referenced in the Firefox advisories. Alongside the security patches, Mozilla’s releases included broad product updates such as privacy and platform changes in Firefox and improved encrypted-message search and OpenPGP features in Thunderbird. Government and Linux distribution advisories urged users and administrators to review Mozilla’s bulletins and apply the latest browser and mail client updates promptly.
Jun 29, 2026