Vulnerability · Published Apr 21, 2026 · Assigned by mozilla
CVE-2026-6762Spoofing issue in the DOM: Core & HTML component
Medium 6.3
In plain English
A medium-severity authentication bypass by spoofing in Firefox from Mozilla. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 8% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)6.3Medium
Exploit odds (30 days)0.2%top 91.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
Spoofing issue in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:10 | firefox | 140.10.0-1.el10_1 | ALSA-2026:10767 |
| AlmaLinux:8 | firefox | 140.10.0-1.el8_10.alma.1 | ALSA-2026:10766 |
| AlmaLinux:9 | firefox | 140.10.0-1.el9_7.alma.1 | ALSA-2026:10757 |
| AlmaLinux:9 | firefox-x11 | 140.10.0-1.el9_7.alma.1 | ALSA-2026:10757 |
| AlmaLinux:10 | thunderbird | 140.10.0-1.el10_1.alma.1 | ALSA-2026:12285 |
| AlmaLinux:8 | thunderbird | 140.10.0-1.el8_10.alma.1 | ALSA-2026:13537 |
| AlmaLinux:9 | thunderbird | 140.10.0-1.el9_7.alma.1 | ALSA-2026:15892 |
| AlmaLinux:9 | thunderbird | 140.10.1-1.el9_8.alma.1 | ALSA-2026:19348 |
| Debian:12 | firefox-esr | 140.10.0esr-1~deb12u1 | DEBIAN-CVE-2026-6762 |
| Debian:13 | firefox-esr | 140.10.0esr-1~deb13u1 | DEBIAN-CVE-2026-6762 |
| Debian:14 | firefox-esr | 140.10.0esr-1 | DEBIAN-CVE-2026-6762 |
| Debian:12 | thunderbird | 1:140.10.0esr-1~deb12u1 | DEBIAN-CVE-2026-6762 |
| Debian:13 | thunderbird | 1:140.10.0esr-1~deb13u1 | DEBIAN-CVE-2026-6762 |
| Debian:14 | thunderbird | 1:140.10.0esr-1 | DEBIAN-CVE-2026-6762 |
| Rocky Linux:10 | firefox | 0:140.10.0-1.el10_1 | RLSA-2026:10767 |
| Rocky Linux:8 | firefox | 0:140.10.0-1.el8_10 | RLSA-2026:10766 |
| Rocky Linux:9 | firefox | 0:140.10.0-1.el9_7 | RLSA-2026:19201 |
| Rocky Linux:9 | firefox | 0:140.10.0-1.el9_7 | RLSA-2026:10757 |
| Rocky Linux:10 | thunderbird | 0:140.10.0-1.el10_1 | RLSA-2026:12285 |
| Rocky Linux:8 | thunderbird | 0:140.10.0-1.el8_10 | RLSA-2026:13537 |
| Rocky Linux:9 | thunderbird | 0:140.10.1-1.el9_8 | RLSA-2026:19348 |
| Rocky Linux:9 | thunderbird | 0:140.10.0-1.el9_7 | RLSA-2026:15892 |
| Ubuntu:22.04:LTS | mozjs102 | no fix listed | UBUNTU-CVE-2026-6762 |
| Ubuntu:24.04:LTS | mozjs102 | no fix listed | UBUNTU-CVE-2026-6762 |
| Ubuntu:24.04:LTS | mozjs115 | no fix listed | UBUNTU-CVE-2026-6762 |
| Ubuntu:22.04:LTS | mozjs78 | no fix listed | UBUNTU-CVE-2026-6762 |
| Ubuntu:22.04:LTS | mozjs91 | no fix listed | UBUNTU-CVE-2026-6762 |
| Ubuntu:22.04:LTS | thunderbird | no fix listed | UBUNTU-CVE-2026-6762 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | see references |
| Mozilla | Thunderbird | see references |
Weakness: CWE-290 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2021080
- https://www.mozilla.org/security/advisories/mfsa2026-30/
- https://www.mozilla.org/security/advisories/mfsa2026-31/
- https://www.mozilla.org/security/advisories/mfsa2026-32/
- https://www.mozilla.org/security/advisories/mfsa2026-33/
- https://www.mozilla.org/security/advisories/mfsa2026-34/