CVE-2026-2776
published 2026-02-24CVE-2026-2776: Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software. This vulnerability was fixed in Firefox 148, Firefox ESR…
PriorityP354critical10CVSS 3.1
AVNACLPRNUINSCCHIHAH
EPSS
0.48%
38.8th percentile
Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.
Affected
13 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | firefox | < firefox 148.0-1 (sid) | firefox 148.0-1 (sid) |
| debian | firefox-esr | < firefox 148.0-1 (sid) | firefox 148.0-1 (sid) |
| debian | thunderbird | < firefox 148.0-1 (sid) | firefox 148.0-1 (sid) |
| mozilla | firefox | < 115.33.0 | 115.33.0 |
| mozilla | firefox | < 148.0 | 148.0 |
| mozilla | firefox | — | — |
| mozilla | firefox | >= 128.0 < 140.8.0 | 140.8.0 |
| mozilla | thunderbird | < 140.8.0 | 140.8.0 |
| mozilla | thunderbird | < 148.0 | 148.0 |
| mozilla | thunderbird | >= 0 < 1:140.8.0esr-1~deb11u1 | 1:140.8.0esr-1~deb11u1 |
| mozilla | thunderbird | >= 0 < 1:140.8.0esr-1~deb12u1 | 1:140.8.0esr-1~deb12u1 |
| mozilla | thunderbird | >= 0 < 1:140.8.0esr-1~deb13u1 | 1:140.8.0esr-1~deb13u1 |
| mozilla | thunderbird | >= 0 < 1:140.8.0esr-1 | 1:140.8.0esr-1 |
CVSS provenance
nvdv3.110.0CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
osv10.0CRITICAL
vendor_debian10.0CRITICAL
vendor_redhat10.0CRITICAL
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Red Hat
firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software
vendor_redhat·2026-02-24·CVSS 10.0
CVE-2026-2776 [CRITICAL] firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software
firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software
Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.
A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue:
Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software
Statement: Red Hat Product Security rates the severity of this flaw as determined by the Mozilla Foundation Security Advisory.
Package: rhel10/firefox-flatpak (Red Hat Enterprise Linux 10) - Affected
Package: rhel10/thunderb
Debian
CVE-2026-2776: firefox - Sandbox escape due to incorrect boundary conditions in the Telemetry component i...
vendor_debian·2026·CVSS 10.0
CVE-2026-2776 [CRITICAL] CVE-2026-2776: firefox - Sandbox escape due to incorrect boundary conditions in the Telemetry component i...
Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.
Scope: local
sid: resolved (fixed in 148.0-1)
Mozilla
Mozilla Foundation Security Advisory 2026-17: CVE-2026-2776
vendor_mozilla·CVSS 10.0
CVE-2026-2776 [CRITICAL] Mozilla Foundation Security Advisory 2026-17: CVE-2026-2776
Mozilla Foundation Security Advisory 2026-17
CVE: CVE-2026-2776
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 140.8
Mozilla
Mozilla Foundation Security Advisory 2026-13: CVE-2026-2776
vendor_mozilla·CVSS 10.0
CVE-2026-2776 [CRITICAL] Mozilla Foundation Security Advisory 2026-13: CVE-2026-2776
Mozilla Foundation Security Advisory 2026-13
CVE: CVE-2026-2776
Product: Firefox
Impact: high
Fixed in: Firefox 148
Mozilla
Mozilla Foundation Security Advisory 2026-15: CVE-2026-2776
vendor_mozilla·CVSS 10.0
CVE-2026-2776 [CRITICAL] Mozilla Foundation Security Advisory 2026-15: CVE-2026-2776
Mozilla Foundation Security Advisory 2026-15
CVE: CVE-2026-2776
Product: Firefox ESR
Impact: high
Fixed in: Firefox ESR 140.8
Mozilla
Mozilla Foundation Security Advisory 2026-16: CVE-2026-2776
vendor_mozilla·CVSS 10.0
CVE-2026-2776 [CRITICAL] Mozilla Foundation Security Advisory 2026-16: CVE-2026-2776
Mozilla Foundation Security Advisory 2026-16
CVE: CVE-2026-2776
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 148
Mozilla
Mozilla Foundation Security Advisory 2026-14: CVE-2026-2776
vendor_mozilla·CVSS 10.0
CVE-2026-2776 [CRITICAL] Mozilla Foundation Security Advisory 2026-14: CVE-2026-2776
Mozilla Foundation Security Advisory 2026-14
CVE: CVE-2026-2776
Product: Firefox ESR
Impact: high
Fixed in: Firefox ESR 115.33
GHSA
GHSA-v33x-35cm-8gjc: Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software
ghsa_unreviewed·2026-02-24
CVE-2026-2776 [CRITICAL] CWE-119 GHSA-v33x-35cm-8gjc: Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software
Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, and Firefox ESR < 140.8.
OSV
CVE-2026-2776: Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software
osv·2026-02-24·CVSS 10.0
CVE-2026-2776 [CRITICAL] CVE-2026-2776: Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software
Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.
No detection rules found.
No public exploits indexed.
Wiz
CVE-2026-2776 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 10.0
CVE-2026-2776 [CRITICAL] CVE-2026-2776 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-2776 :
NixOS vulnerability analysis and mitigation
Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.
Source : NVD
## 10
Score
Published February 24, 2026
Severity CRITICAL
CNA Score 10.0
Affected Technologies
NixOS
Mozilla Firefox
Has Public Exploit No
Has CISA KEV Exploit No
CISA KEV Release Date N/A
CISA KEV Due Date N/A
Exploitation Probability Percentile (EPSS) 23
Exploitation Probability (EPSS) 0.1
Affected packages and libraries
MozillaThunderbird
thunderbird
Sources
AlmaLinux 8 Severity HIGH Has Fix Added at: Mar 03, 2026
AlmaLinux 9 Severity HIGH Has Fix Added at: Mar
Bugzilla
CVE-2026-2776 firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software
bugzilla·2026-02-24·CVSS 10.0
CVE-2026-2776 [CRITICAL] CVE-2026-2776 firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software
CVE-2026-2776 firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software
Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, and Firefox ESR < 140.8.
Discussion:
This issue has been addressed in the following products:
Red Hat Enterprise Linux 8
Via RHSA-2026:3338 https://access.redhat.com/errata/RHSA-2026:3338
---
This issue has been addressed in the following products:
Red Hat Enterprise Linux 9
Via RHSA-2026:3339 https://access.redhat.com/errata/RHSA-2026:3339
---
This issue has been addressed in the following products:
Red Hat Enterprise Linux 10
Via RHSA-2026:3361 https://access.redhat.com/errata/RH
https://bugzilla.mozilla.org/show_bug.cgi?id=2015266https://www.mozilla.org/security/advisories/mfsa2026-13/https://www.mozilla.org/security/advisories/mfsa2026-14/https://www.mozilla.org/security/advisories/mfsa2026-15/https://www.mozilla.org/security/advisories/mfsa2026-16/https://www.mozilla.org/security/advisories/mfsa2026-17/https://access.redhat.com/errata/RHSA-2026:3338https://access.redhat.com/errata/RHSA-2026:3339https://access.redhat.com/errata/RHSA-2026:3361https://access.redhat.com/errata/RHSA-2026:3491https://access.redhat.com/errata/RHSA-2026:3492https://access.redhat.com/errata/RHSA-2026:3493https://access.redhat.com/errata/RHSA-2026:3494https://access.redhat.com/errata/RHSA-2026:3495https://access.redhat.com/errata/RHSA-2026:3496https://access.redhat.com/errata/RHSA-2026:3497https://access.redhat.com/errata/RHSA-2026:3515https://access.redhat.com/errata/RHSA-2026:3516https://access.redhat.com/errata/RHSA-2026:3517https://access.redhat.com/errata/RHSA-2026:3976https://access.redhat.com/errata/RHSA-2026:3978https://access.redhat.com/errata/RHSA-2026:3979https://access.redhat.com/errata/RHSA-2026:3980https://access.redhat.com/errata/RHSA-2026:3981https://access.redhat.com/errata/RHSA-2026:3982https://access.redhat.com/errata/RHSA-2026:3983https://access.redhat.com/errata/RHSA-2026:3984https://access.redhat.com/errata/RHSA-2026:4022https://access.redhat.com/errata/RHSA-2026:4152https://access.redhat.com/errata/RHSA-2026:4260https://access.redhat.com/errata/RHSA-2026:4432https://access.redhat.com/security/cve/CVE-2026-2776https://bugzilla.redhat.com/show_bug.cgi?id=2442291https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-2776.json
2026-02-24
Published