CVE-2026-84143
published 2026-09-01CVE-2026-84143: Internally found bugs present in Thunderbird 154, Thunderbird ESR 153.1 and Thunderbird ESR 140.14. Some of these bugs showed evidence of memory corruption or…
PriorityP351critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EPSS
0.38%
31.1th percentile
Internally found bugs present in Thunderbird 154, Thunderbird ESR 153.1 and Thunderbird ESR 140.14. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 155, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.
Affected
16 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| mozilla | firefox | < Firefox 155 | Firefox 155 |
| mozilla | firefox | < 140.15.0 | 140.15.0 |
| mozilla | firefox | — | — |
| mozilla | firefox | >= 141.0.0 < 153.2.0 | 153.2.0 |
| mozilla | firefox | >= 154.0.0 < 155.0.0 | 155.0.0 |
| mozilla | firefox_esr | < Firefox ESR 140.15 | Firefox ESR 140.15 |
| mozilla | firefox_esr | < Firefox ESR 153.2 | Firefox ESR 153.2 |
| mozilla | thunderbird | < Thunderbird 140.15 | Thunderbird 140.15 |
| mozilla | thunderbird | < Thunderbird 153.2 | Thunderbird 153.2 |
| mozilla | thunderbird | < Thunderbird 155 | Thunderbird 155 |
| mozilla | thunderbird | < 140.15.0 | 140.15.0 |
| mozilla | thunderbird | — | — |
| mozilla | thunderbird | >= 141.0 < 153.2.0 | 153.2.0 |
| mozilla | thunderbird | >= 154.0 < 155.0 | 155.0 |
| rhel10 | firefox-flatpak | — | — |
| rhel10 | thunderbird-flatpak | — | — |
CVSS provenance
nvdv3.19.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vendor_redhat9.8CRITICAL
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VulDB
Mozilla Firefox up to 140.14/153.1/154 memory corruption (Nessus ID 342306)
vuldb·2026-09-03
CVE-2026-84143 [CRITICAL] Mozilla Firefox up to 140.14/153.1/154 memory corruption (Nessus ID 342306)
A vulnerability, which was classified as critical, has been found in Mozilla Firefox up to 140.14/153.1/154. This impacts an unknown function. This manipulation causes memory corruption.
This vulnerability is registered as CVE-2026-84143. Remote exploitation of the attack is possible. No exploit is available.
It is advisable to upgrade the affected component.
GHSA
Internally found bugs present in Firefox 154, Firefox ESR 153.1 and Firefox ESR 140.14.
ghsa_unreviewed·2026-09-01
CVE-2026-84143 Internally found bugs present in Firefox 154, Firefox ESR 153.1 and Firefox ESR 140.14.
Internally found bugs present in Firefox 154, Firefox ESR 153.1 and Firefox ESR 140.14. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 155, Firefox ESR 140.15, and Firefox ESR 153.2.
Red Hat
firefox: Internally found bugs fixed in Firefox 155, Firefox ESR 153.2 and Firefox ESR 140.15
vendor_redhat·2026-09-01·CVSS 9.8
CVE-2026-84143 [CRITICAL] CWE-787 firefox: Internally found bugs fixed in Firefox 155, Firefox ESR 153.2 and Firefox ESR 140.15
firefox: Internally found bugs fixed in Firefox 155, Firefox ESR 153.2 and Firefox ESR 140.15
Internally found bugs present in Thunderbird 154, Thunderbird ESR 153.1 and Thunderbird ESR 140.14. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 155, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.
A flaw was found in Firefox. The Mozilla Foundation's Security Advisory describes the following issue:
Internally found bugs present in Firefox 154, Firefox ESR 153.1 and Firefox ESR 140.14. Some of these bugs showed evidence of memory corruption or another security-relevant defect and w
Mozilla
Mozilla Foundation Security Advisory 2026-84: CVE-2026-84143
vendor_mozilla
CVE-2026-84143 Mozilla Foundation Security Advisory 2026-84: CVE-2026-84143
Mozilla Foundation Security Advisory 2026-84
CVE: CVE-2026-84143
Product: Firefox ESR
Impact: high
Fixed in: Firefox ESR 140.15
Mozilla
Mozilla Foundation Security Advisory 2026-87: CVE-2026-84143
vendor_mozilla
CVE-2026-84143 Mozilla Foundation Security Advisory 2026-87: CVE-2026-84143
Mozilla Foundation Security Advisory 2026-87
CVE: CVE-2026-84143
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 140.15
Mozilla
Mozilla Foundation Security Advisory 2026-82: CVE-2026-84143
vendor_mozilla
CVE-2026-84143 Mozilla Foundation Security Advisory 2026-82: CVE-2026-84143
Mozilla Foundation Security Advisory 2026-82
CVE: CVE-2026-84143
Product: Firefox
Impact: high
Fixed in: Firefox 155
Mozilla
Mozilla Foundation Security Advisory 2026-88: CVE-2026-84143
vendor_mozilla
CVE-2026-84143 Mozilla Foundation Security Advisory 2026-88: CVE-2026-84143
Mozilla Foundation Security Advisory 2026-88
CVE: CVE-2026-84143
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 153.2
Mozilla
Mozilla Foundation Security Advisory 2026-86: CVE-2026-84143
vendor_mozilla
CVE-2026-84143 Mozilla Foundation Security Advisory 2026-86: CVE-2026-84143
Mozilla Foundation Security Advisory 2026-86
CVE: CVE-2026-84143
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 155
Mozilla
Mozilla Foundation Security Advisory 2026-85: CVE-2026-84143
vendor_mozilla
CVE-2026-84143 Mozilla Foundation Security Advisory 2026-85: CVE-2026-84143
Mozilla Foundation Security Advisory 2026-85
CVE: CVE-2026-84143
Product: Firefox ESR
Impact: high
Fixed in: Firefox ESR 153.2
No detection rules found.
No public exploits indexed.
https://bugzilla.mozilla.org/buglist.cgi?bug_id=2048793%2C2054645%2C2057114%2C2059109%2C2061287https://bugzilla.mozilla.org/buglist.cgi?bug_id=2054631%2C2054657%2C2055007%2C2055681%2C2057107%2C2058087%2C2058088%2C2058090%2C2058095%2C2058101%2C2059183%2C2059185%2C2061301%2C2061325https://bugzilla.mozilla.org/show_bug.cgi?id=2057108https://www.mozilla.org/security/advisories/mfsa2026-82/https://www.mozilla.org/security/advisories/mfsa2026-84/https://www.mozilla.org/security/advisories/mfsa2026-85/https://www.mozilla.org/security/advisories/mfsa2026-86/https://www.mozilla.org/security/advisories/mfsa2026-87/https://www.mozilla.org/security/advisories/mfsa2026-88/
2026-09-01
Published