CVE-2026-84142
published 2026-09-01CVE-2026-84142: Internally found bugs present in Thunderbird 154. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume…
PriorityP348critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EPSS
0.56%
45.0th percentile
Internally found bugs present in Thunderbird 154. 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 and Thunderbird 155.
Affected
4 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| mozilla | firefox | < Firefox 155 | Firefox 155 |
| mozilla | firefox | < 155.0.0 | 155.0.0 |
| mozilla | thunderbird | < Thunderbird 155 | Thunderbird 155 |
| mozilla | thunderbird | < 155.0 | 155.0 |
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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Red Hat
firefox: thunderbird: Internally found bugs fixed in Firefox 155
vendor_redhat·2026-09-01·CVSS 9.8
CVE-2026-84142 [CRITICAL] CWE-787 firefox: thunderbird: Internally found bugs fixed in Firefox 155
firefox: thunderbird: Internally found bugs fixed in Firefox 155
Internally found bugs present in Thunderbird 154. 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 and Thunderbird 155.
A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue:
Internally found bugs present in Thunderbird 154. 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.
Statement: Red Hat Product Security rates the severity of this flaw as determined by the Mozilla Foundat
Mozilla
Mozilla Foundation Security Advisory 2026-82: CVE-2026-84142
vendor_mozilla
CVE-2026-84142 Mozilla Foundation Security Advisory 2026-82: CVE-2026-84142
Mozilla Foundation Security Advisory 2026-82
CVE: CVE-2026-84142
Product: Firefox
Impact: high
Fixed in: Firefox 155
Mozilla
Mozilla Foundation Security Advisory 2026-86: CVE-2026-84142
vendor_mozilla
CVE-2026-84142 Mozilla Foundation Security Advisory 2026-86: CVE-2026-84142
Mozilla Foundation Security Advisory 2026-86
CVE: CVE-2026-84142
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 155
GHSA
Internally found bugs present in Firefox 154.
ghsa_unreviewed·2026-09-01
CVE-2026-84142 Internally found bugs present in Firefox 154.
Internally found bugs present in Firefox 154. 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.
No detection rules found.
No public exploits indexed.
https://bugzilla.mozilla.org/buglist.cgi?bug_id=2029421%2C2040889%2C2045313%2C2045435%2C2053578%2C2058621%2C2058626https://bugzilla.mozilla.org/buglist.cgi?bug_id=2048796%2C2053150%2C2057356https://www.mozilla.org/security/advisories/mfsa2026-82/https://www.mozilla.org/security/advisories/mfsa2026-86/
2026-09-01
Published