# Mozilla Thunderbird (rm) 155.0 Mozilla Thunderbird (rm) 155.0, released September 1, 2026, fixes 31 CVEs in Mozilla Thunderbird (rm). None of them is reported as exploited. Patch Radar priority: Urgent. The latest Mozilla Thunderbird (rm) is 159.0, which also fixes every one of these CVEs. - Web page: https://patchblox.com/security/fix/windows-app/mozilla.thunderbird.rm-155.0 - Platform: Windows apps - Released: Sep 1, 2026 - Priority: Urgent (Closes CVE-2026-84637, rated Critical) - CVEs: 31, exploited: 0, on CISA KEV: 0 - Superseded by: [Mozilla Thunderbird (rm) 159.0](https://patchblox.com/security/data/product/windows-app/mozilla-thunderbird-rm.md), the latest version, which also fixes every CVE listed here ## Applies to | Product | Release | Fixed in | |---|---|---| | [Mozilla Thunderbird (rm)](https://patchblox.com/security/data/product/windows-app/mozilla-thunderbird-rm.md) | | 155.0 | ## CVEs this fix closes | CVE | Priority | Title | CVSS | EPSS | Exploitation | |---|---|---|---:|---:|---| | [CVE-2026-84637](https://patchblox.com/security/data/cve/CVE-2026-84637.md) | Urgent | Calendar invitation attachments could launch local executables | 9.8 | 0.0063 | | | [CVE-2026-84134](https://patchblox.com/security/data/cve/CVE-2026-84134.md) | Urgent | Other issue in the Profile Backup component | 9.8 | 0.0057 | | | [CVE-2026-84142](https://patchblox.com/security/data/cve/CVE-2026-84142.md) | Urgent | Internally found bugs fixed in Thunderbird 155 | 9.8 | 0.0056 | | | [CVE-2026-84143](https://patchblox.com/security/data/cve/CVE-2026-84143.md) | Urgent | Internally found bugs fixed in Thunderbird 155, Thunderbird ESR 153.2 and Thunderbird ESR 140.15 | 9.8 | 0.0038 | | | [CVE-2026-84639](https://patchblox.com/security/data/cve/CVE-2026-84639.md) | Urgent | Uninitialized memory in MIME parsing | 9.1 | 0.0032 | | | [CVE-2026-84119](https://patchblox.com/security/data/cve/CVE-2026-84119.md) | Urgent | Sandbox escape due to use-after-free in the DOM: Navigation component | 9.6 | 0.0032 | | | [CVE-2026-84121](https://patchblox.com/security/data/cve/CVE-2026-84121.md) | Urgent | Sandbox escape due to use-after-free in the DOM: Security component | 9.6 | 0.0032 | | | [CVE-2026-84130](https://patchblox.com/security/data/cve/CVE-2026-84130.md) | High | Information disclosure in the Graphics: WebGPU component | 7.5 | 0.0044 | | | [CVE-2026-84128](https://patchblox.com/security/data/cve/CVE-2026-84128.md) | High | Privilege escalation in the WebDriver BiDi component | 8.8 | 0.0044 | | | [CVE-2026-84123](https://patchblox.com/security/data/cve/CVE-2026-84123.md) | High | Privilege escalation due to use-after-free in the Graphics: WebGPU component | 8.8 | 0.0044 | | | [CVE-2026-84144](https://patchblox.com/security/data/cve/CVE-2026-84144.md) | High | Internally found bugs fixed in Thunderbird 155 and Thunderbird ESR 153.2 | 7.5 | 0.0043 | | | [CVE-2026-84642](https://patchblox.com/security/data/cve/CVE-2026-84642.md) | High | Allowed UNC hostnames for attachments interpreted as a regular expression | 7.5 | 0.0042 | | | [CVE-2026-84145](https://patchblox.com/security/data/cve/CVE-2026-84145.md) | High | Internally found bugs fixed in Thunderbird 155, Thunderbird ESR 153.2 and Thunderbird ESR 140.15 | 7.5 | 0.0037 | | | [CVE-2026-84141](https://patchblox.com/security/data/cve/CVE-2026-84141.md) | High | Integer overflow in the Graphics: ImageLib component | 9.8 | 0.0034 | | | [CVE-2026-84131](https://patchblox.com/security/data/cve/CVE-2026-84131.md) | High | Privilege escalation due to invalid pointer in the Graphics component | 8.8 | 0.0033 | | | [CVE-2026-84641](https://patchblox.com/security/data/cve/CVE-2026-84641.md) | High | Information disclosure due to malicious IMAP server response | 7.5 | 0.0027 | | | [CVE-2026-84640](https://patchblox.com/security/data/cve/CVE-2026-84640.md) | High | One byte overflow read in mail parser | 7.5 | 0.0026 | | | [CVE-2026-84132](https://patchblox.com/security/data/cve/CVE-2026-84132.md) | High | Information disclosure in the Networking: HTTP component | 7.5 | 0.0026 | | | [CVE-2026-84120](https://patchblox.com/security/data/cve/CVE-2026-84120.md) | High | Use-after-free in the Audio/Video component | 7.5 | 0.0022 | | | [CVE-2026-84122](https://patchblox.com/security/data/cve/CVE-2026-84122.md) | High | Use-after-free in the Audio/Video component | 7.5 | 0.0021 | | | [CVE-2026-84129](https://patchblox.com/security/data/cve/CVE-2026-84129.md) | High | Site isolation issue in the DOM: Navigation component | 9.8 | 0.0019 | | | [CVE-2026-84133](https://patchblox.com/security/data/cve/CVE-2026-84133.md) | High | Site isolation issue in the DOM: Push Subscriptions component | 9.8 | 0.0019 | | | [CVE-2026-84140](https://patchblox.com/security/data/cve/CVE-2026-84140.md) | High | Site isolation issue in the DOM: Navigation component | 9.8 | 0.0018 | | | [CVE-2026-84124](https://patchblox.com/security/data/cve/CVE-2026-84124.md) | High | Use-after-free in the DOM: Core & HTML component | 8.8 | 0.0017 | | | [CVE-2026-84138](https://patchblox.com/security/data/cve/CVE-2026-84138.md) | Routine | Denial-of-service in the PDF Viewer component | 6.5 | 0.0037 | | | [CVE-2026-84139](https://patchblox.com/security/data/cve/CVE-2026-84139.md) | Routine | Clickjacking issue in the DOM: Events component | 6.1 | 0.0034 | | | [CVE-2026-84126](https://patchblox.com/security/data/cve/CVE-2026-84126.md) | Routine | Incorrect boundary conditions in the Layout: Grid component | 4.3 | 0.0031 | | | [CVE-2026-84118](https://patchblox.com/security/data/cve/CVE-2026-84118.md) | Routine | Use-after-free in the JavaScript: GC component | 5.4 | 0.0029 | | | [CVE-2026-84125](https://patchblox.com/security/data/cve/CVE-2026-84125.md) | Routine | Use-after-free in the DOM: Core & HTML component | 5.4 | 0.0029 | | | [CVE-2026-84136](https://patchblox.com/security/data/cve/CVE-2026-84136.md) | Routine | Other issue in the DOM: Navigation component | 6.1 | 0.0020 | | | [CVE-2026-84137](https://patchblox.com/security/data/cve/CVE-2026-84137.md) | Routine | Spoofing issue in the DOM: Core & HTML component | 4.3 | 0.0013 | | --- Data as of 2026-11-09T19:38:12Z UTC. 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