Mozilla Firefox 155.0
Mozilla Firefox 155.0, released August 26, 2026, fixes 26 CVEs in Mozilla Firefox. None of them is reported as exploited. Patch Radar priority: Urgent. The latest Mozilla Firefox is 159.0.1, which also fixes every one of these CVEs.
Superseded. The latest Mozilla Firefox is 159.0.1, which also fixes every CVE on this page. Install that instead.
Priority of the 26 CVEs
Applies to
| Product | Version |
|---|---|
| Mozilla Firefox | 155.0 |
CVEs this fix closes
| Priority | CVE | Title | CVSS | EPSS | Exploitation |
|---|---|---|---|---|---|
| Urgent | CVE-2026-84134 | Other issue in the Profile Backup component | 9.8 | 0.0057 | None reported |
| Urgent | CVE-2026-84142 | Internally found bugs fixed in Thunderbird 155 | 9.8 | 0.0056 | None reported |
| Urgent | CVE-2026-84143 | Internally found bugs fixed in Thunderbird 155, Thunderbird ESR 153.2 and Thunderbird ESR 140.15 | 9.8 | 0.0038 | None reported |
| Urgent | CVE-2026-84119 | Sandbox escape due to use-after-free in the DOM: Navigation component | 9.6 | 0.0032 | None reported |
| Urgent | CVE-2026-84121 | Sandbox escape due to use-after-free in the DOM: Security component | 9.6 | 0.0032 | None reported |
| High | CVE-2026-84130 | Information disclosure in the Graphics: WebGPU component | 7.5 | 0.0044 | None reported |
| High | CVE-2026-84128 | Privilege escalation in the WebDriver BiDi component | 8.8 | 0.0044 | None reported |
| High | CVE-2026-84123 | Privilege escalation due to use-after-free in the Graphics: WebGPU component | 8.8 | 0.0044 | None reported |
| High | CVE-2026-84144 | Internally found bugs fixed in Thunderbird 155 and Thunderbird ESR 153.2 | 7.5 | 0.0043 | None reported |
| High | CVE-2026-84145 | Internally found bugs fixed in Thunderbird 155, Thunderbird ESR 153.2 and Thunderbird ESR 140.15 | 7.5 | 0.0037 | None reported |
| High | CVE-2026-84141 | Integer overflow in the Graphics: ImageLib component | 9.8 | 0.0034 | None reported |
| High | CVE-2026-84131 | Privilege escalation due to invalid pointer in the Graphics component | 8.8 | 0.0033 | None reported |
| High | CVE-2026-84132 | Information disclosure in the Networking: HTTP component | 7.5 | 0.0026 | None reported |
| High | CVE-2026-84120 | Use-after-free in the Audio/Video component | 7.5 | 0.0022 | None reported |
| High | CVE-2026-84122 | Use-after-free in the Audio/Video component | 7.5 | 0.0021 | None reported |
| High | CVE-2026-84129 | Site isolation issue in the DOM: Navigation component | 9.8 | 0.0019 | None reported |
| High | CVE-2026-84133 | Site isolation issue in the DOM: Push Subscriptions component | 9.8 | 0.0019 | None reported |
| High | CVE-2026-84140 | Site isolation issue in the DOM: Navigation component | 9.8 | 0.0018 | None reported |
| High | CVE-2026-84124 | Use-after-free in the DOM: Core & HTML component | 8.8 | 0.0017 | None reported |
| Routine | CVE-2026-84138 | Denial-of-service in the PDF Viewer component | 6.5 | 0.0037 | None reported |
| Routine | CVE-2026-84139 | Clickjacking issue in the DOM: Events component | 6.1 | 0.0034 | None reported |
| Routine | CVE-2026-84126 | Incorrect boundary conditions in the Layout: Grid component | 4.3 | 0.0031 | None reported |
| Routine | CVE-2026-84118 | Use-after-free in the JavaScript: GC component | 5.4 | 0.0029 | None reported |
| Routine | CVE-2026-84125 | Use-after-free in the DOM: Core & HTML component | 5.4 | 0.0029 | None reported |
| Routine | CVE-2026-84136 | Other issue in the DOM: Navigation component | 6.1 | 0.0020 | None reported |
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