Race condition in Mozilla Thunderbird
Priority LOW 23CWE-362Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Required
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- None · Low · None
- Fix status
- Partial Red Hat: 10 fixed, 1 without a fix
Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat.
Summary
By misusing a race in our notification code, an attacker could have forcefully hidden the notification for pages that had received full screen and pointer lock access, which could have been used for spoofing attacks. This vulnerability affects Thunderbird < 91.4.0, Firefox ESR < 91.4.0, and Firefox < 95.
Why it matters now
EPSS 0.01245 69th percentileScored 2026-11-07
Fix Partial Thunderbird (Mozilla): 91.4.0Firefox ESR (Mozilla): 91.4.0+1 more productRed Hat: 10 advisoriesRed Hat: 10 fixed, 1 without a fix
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Mozilla | Thunderbird | before 91.4.0 | 91.4.0 | Patch available | CNA |
| Mozilla | Firefox ESR | before 91.4.0 | 91.4.0 | Patch available | CNA |
| Mozilla | Firefox | before 95 | 95 | Patch available | CNA |
- Thunderbird VendorMozilla Affected before 91.4.0 Fixed in 91.4.0 Patch available CNA
- Firefox ESR VendorMozilla Affected before 91.4.0 Fixed in 91.4.0 Patch available CNA
- Firefox VendorMozilla Affected before 95 Fixed in 95 Patch available CNA
CPE configurations NVD · 6
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* | before 95.0 | Vulnerable | Mozilla |
| cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:* | before 91.4.0 | Vulnerable | Mozilla |
| cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* | before 91.4.0 | Vulnerable | Mozilla |
| cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:* | 9.0 | Vulnerable | Debian |
| cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:* | 10.0 | Vulnerable | Debian |
| cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:* | 11.0 | Vulnerable | Debian |
- cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* Versions before 95.0 Vulnerable ·Mozilla
- cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:* Versions before 91.4.0 Vulnerable ·Mozilla
- cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* Versions before 91.4.0 Vulnerable ·Mozilla
- cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:* Versions 9.0 Vulnerable ·Debian
- cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:* Versions 10.0 Vulnerable ·Debian
- cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:* Versions 11.0 Vulnerable ·Debian
Remediation
- Fix · CNA Thunderbird (Mozilla) Fixed in 91.4.0
- Fix · CNA Firefox ESR (Mozilla) Fixed in 91.4.0
- Fix · CNA Firefox (Mozilla) Fixed in 95
Red Hat 10 advisories
- RHSA-2021:5055 Released 2021-12-09 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux AppStream E4S (v. 8.1) thunderbird-91.4.0-2.el8_1
- RHSA-2021:5046 Released 2021-12-09 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux Client (v. 7) thunderbird-91.4.0-3.el7_9
- Red Hat Enterprise Linux Server Optional (v. 7) thunderbird-91.4.0-3.el7_9
- Red Hat Enterprise Linux Workstation (v. 7) thunderbird-91.4.0-3.el7_9
- RHSA-2021:5048 Released 2021-12-09 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux AppStream EUS (v.8.4) thunderbird-91.4.0-2.el8_4
Show 7 more Red Hat advisories
- RHSA-2021:5045 Released 2021-12-09 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux AppStream (v. 8) thunderbird-91.4.0-2.el8_5
- RHSA-2021:5047 Released 2021-12-09 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux AppStream EUS (v. 8.2) thunderbird-91.4.0-2.el8_2
- RHSA-2021:5014 Released 2021-12-08 · Red Hat rating Importantfirefox security update
- Red Hat Enterprise Linux Client (v. 7) firefox-91.4.0-1.el7_9
- Red Hat Enterprise Linux Client Optional (v. 7) firefox-91.4.0-1.el7_9
- Red Hat Enterprise Linux Server (v. 7) firefox-91.4.0-1.el7_9
- Red Hat Enterprise Linux Server Optional (v. 7) firefox-91.4.0-1.el7_9
- Red Hat Enterprise Linux Workstation (v. 7) firefox-91.4.0-1.el7_9
- Red Hat Enterprise Linux Workstation Optional (v. 7) firefox-91.4.0-1.el7_9
- RHSA-2021:5016 Released 2021-12-08 · Red Hat rating Importantfirefox security update
- Red Hat Enterprise Linux AppStream EUS (v. 8.2) firefox-91.4.0-1.el8_2
- RHSA-2021:5015 Released 2021-12-08 · Red Hat rating Importantfirefox security update
- Red Hat Enterprise Linux AppStream EUS (v.8.4) firefox-91.4.0-1.el8_4
- RHSA-2021:5013 Released 2021-12-08 · Red Hat rating Importantfirefox security update
- Red Hat Enterprise Linux AppStream (v. 8) firefox-91.4.0-1.el8_5
- RHSA-2021:5017 Released 2021-12-08 · Red Hat rating Importantfirefox security update
- Red Hat Enterprise Linux AppStream E4S (v. 8.1) firefox-91.4.0-1.el8_1
Fixed in the same release
Records fixed by the same vendor advisory or release, as the CNA lists them.
- Advisory ·
Mozilla Firefox, Firefox ESR, Thunderbird — DSA-5026
17 records Highest priority Priority MEDIUM 6 MEDIUM, 11 LOW
Other records, highest priority first
- TI-2021-16103 Incorrect authorization in Mozilla FirefoxPriority MEDIUM 50
- TI-2021-19429 Use after free in Mozilla ThunderbirdPriority MEDIUM 42
- TI-2021-19427 Incorrect type conversion in Mozilla ThunderbirdPriority MEDIUM 42
Vendor assessments
Red Hat
Red Hat rating: Important. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux AppStream (v. 8) | Fixed | RHSA-2021:5013, RHSA-2021:5045 |
| Red Hat Enterprise Linux AppStream E4S (v. 8.1) | Fixed | RHSA-2021:5017, RHSA-2021:5055 |
| Red Hat Enterprise Linux AppStream EUS (v. 8.2) | Fixed | RHSA-2021:5016, RHSA-2021:5047 |
| Red Hat Enterprise Linux AppStream EUS (v.8.4) | Fixed | RHSA-2021:5015, RHSA-2021:5048 |
| Red Hat Enterprise Linux Client (v. 7) | Fixed | RHSA-2021:5014, RHSA-2021:5046 |
| Red Hat Enterprise Linux Client Optional (v. 7) | Fixed | RHSA-2021:5014 |
| Red Hat Enterprise Linux Server (v. 7) | Fixed | RHSA-2021:5014 |
| Red Hat Enterprise Linux Server Optional (v. 7) | Fixed | RHSA-2021:5014, RHSA-2021:5046 |
| Red Hat Enterprise Linux Workstation (v. 7) | Fixed | RHSA-2021:5014, RHSA-2021:5046 |
| Red Hat Enterprise Linux Workstation Optional (v. 7) | Fixed | RHSA-2021:5014 |
Timeline
- 2026-10-02 Threatist record created from CVE-2021-43538
- 2026-10-03 Alias added: GHSA-9mvw-9c9q-7cmm
References
Advisory 10
- https://www.mozilla.org/security/advisories/mfsa2021-53/
- https://www.mozilla.org/security/advisories/mfsa2021-54/
- https://www.mozilla.org/security/advisories/mfsa2021-52/
- https://bugzilla.mozilla.org/show_bug.cgi?id=1739091
- DSA-5026
- [debian-lts-announce] 20211229 [SECURITY] [DLA 2863-1] firefox-esr security update
- DSA-5034
- [debian-lts-announce] 20220104 [SECURITY] [DLA 2874-1] thunderbird security update
- GLSA-202202-03
- GLSA-202208-14
More Mozilla Firefox vulnerabilities
- TI-2024-08981 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.8
- TI-2022-09832 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.6
- TI-2019-08769 Improper input validation in Mozilla Firefox ESR KEVCVSS 3.1CRITICAL 10.0
- TI-2010-03577 Mozilla Firefox 3.5.x through 3.5.14 and 3.6.x through 3.6.11, Thunderbird 3.1.6 before… KEVCVSS 3.1CRITICAL 9.8
- TI-2023-04799 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8
- TI-2023-04477 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8
Sources
- CVE-2021-43538 · CVE Program
- CVE-2021-43538 · NVD
- FIRST EPSS
- GHSA-9mvw-9c9q-7cmm · GitHub Advisory Database · CC BY 4.0
- CVE-2021-43538 · Red Hat security data · CC BY 4.0
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