Use after free in Mozilla Firefox
Priority MEDIUM 42CWE-416Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Required
- Attack complexity
- Low
- Impact type
- Code execution
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Partial Red Hat: 16 fixed, 1 without a fix
Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-416 and the CVSS impact.
Summary
Mozilla developers reported memory safety bugs present in Firefox 80 and Firefox ESR 78.2. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 81, Thunderbird < 78.3, and Firefox ESR < 78.3.
Why it matters now
EPSS 0.01961 80th percentileScored 2026-11-07
Fix Partial Firefox (Mozilla): 81Thunderbird (Mozilla): 78.3+1 more productRed Hat: 10 advisoriesRed Hat: 16 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 | Firefox | before 81 | 81 | Patch available | CNA |
| Mozilla | Thunderbird | before 78.3 | 78.3 | Patch available | CNA |
| Mozilla | Firefox ESR | before 78.3 | 78.3 | Patch available | CNA |
- Firefox VendorMozilla Affected before 81 Fixed in 81 Patch available CNA
- Thunderbird VendorMozilla Affected before 78.3 Fixed in 78.3 Patch available CNA
- Firefox ESR VendorMozilla Affected before 78.3 Fixed in 78.3 Patch available CNA
CPE configurations NVD · 7
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* | before 81.0 | Vulnerable | Mozilla |
| cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:* | before 78.3 | Vulnerable | Mozilla |
| cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* | before 78.3 | 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:opensuse:leap:15.1:*:*:*:*:*:*:* | 15.1 | Vulnerable | openSUSE |
| cpe:2.3:o:opensuse:leap:15.2:*:*:*:*:*:*:* | 15.2 | Vulnerable | openSUSE |
- cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* Versions before 81.0 Vulnerable ·Mozilla
- cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:* Versions before 78.3 Vulnerable ·Mozilla
- cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* Versions before 78.3 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:opensuse:leap:15.1:*:*:*:*:*:*:* Versions 15.1 Vulnerable ·openSUSE
- cpe:2.3:o:opensuse:leap:15.2:*:*:*:*:*:*:* Versions 15.2 Vulnerable ·openSUSE
Remediation
- Fix · CNA Firefox (Mozilla) Fixed in 81
- Fix · CNA Thunderbird (Mozilla) Fixed in 78.3
- Fix · CNA Firefox ESR (Mozilla) Fixed in 78.3
Red Hat 10 advisories
- RHSA-2020:4163 Released 2020-10-01 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux Client (v. 7) thunderbird-78.3.1-1.el7_9
- Red Hat Enterprise Linux Server Optional (v. 7) thunderbird-78.3.1-1.el7_9
- Red Hat Enterprise Linux Workstation (v. 7) thunderbird-78.3.1-1.el7_9
- RHSA-2020:4158 Released 2020-10-01 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux Desktop (v. 6) thunderbird-78.3.1-1.el6_10
- Red Hat Enterprise Linux Server Optional (v. 6) thunderbird-78.3.1-1.el6_10
- Red Hat Enterprise Linux Workstation (v. 6) thunderbird-78.3.1-1.el6_10
- RHSA-2020:4155 Released 2020-10-01 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux AppStream (v. 8) thunderbird-78.3.1-1.el8_2
Show 7 more Red Hat advisories
- RHSA-2020:4157 Released 2020-10-01 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux AppStream EUS (v. 8.1) thunderbird-78.3.1-1.el8_1
- RHSA-2020:4156 Released 2020-10-01 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux AppStream E4S (v. 8.0) thunderbird-78.3.1-1.el8_0
- RHSA-2020:4080 Released 2020-09-30 · Red Hat rating Importantfirefox security and bug fix update
- Red Hat Enterprise Linux Client (v. 7) firefox-78.3.0-1.el7_9
- Red Hat Enterprise Linux Client Optional (v. 7) firefox-78.3.0-1.el7_9
- Red Hat Enterprise Linux Server (v. 7) firefox-78.3.0-1.el7_9
- Red Hat Enterprise Linux Server Optional (v. 7) firefox-78.3.0-1.el7_9
- Red Hat Enterprise Linux Workstation (v. 7) firefox-78.3.0-1.el7_9
- Red Hat Enterprise Linux Workstation Optional (v. 7) firefox-78.3.0-1.el7_9
- RHSA-2020:3835 Released 2020-09-24 · Red Hat rating Importantfirefox security update
- Red Hat Enterprise Linux Desktop (v. 6) firefox-78.3.0-1.el6_10
- Red Hat Enterprise Linux Desktop Optional (v. 6) firefox-78.3.0-1.el6_10
- Red Hat Enterprise Linux HPC Node Optional (v. 6) firefox-78.3.0-1.el6_10
- Red Hat Enterprise Linux Server (v. 6) firefox-78.3.0-1.el6_10
- Red Hat Enterprise Linux Server Optional (v. 6) firefox-78.3.0-1.el6_10
- Red Hat Enterprise Linux Workstation (v. 6) firefox-78.3.0-1.el6_10
- Red Hat Enterprise Linux Workstation Optional (v. 6) firefox-78.3.0-1.el6_10
- RHSA-2020:3832 Released 2020-09-24 · Red Hat rating Importantfirefox security update
- Red Hat Enterprise Linux AppStream (v. 8) firefox-78.3.0-1.el8_2
- RHSA-2020:3833 Released 2020-09-24 · Red Hat rating Importantfirefox security update
- Red Hat Enterprise Linux AppStream EUS (v. 8.1) firefox-78.3.0-1.el8_1
- RHSA-2020:3834 Released 2020-09-24 · Red Hat rating Importantfirefox security update
- Red Hat Enterprise Linux AppStream E4S (v. 8.0) firefox-78.3.0-1.el8_0
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 — openSUSE-SU-2020:1780
4 records Highest priority Priority MEDIUM 2 MEDIUM, 2 LOW
Other records, highest priority first
- TI-2020-12352 Use after free in Mozilla FirefoxPriority MEDIUM 42
- TI-2020-12351 Open redirect in Mozilla FirefoxPriority LOW 31
- TI-2020-12350 Cross-site scripting in Mozilla FirefoxPriority LOW 30
- Advisory ·
Mozilla Firefox, Firefox ESR, Thunderbird — openSUSE-SU-2020:1785
4 records Highest priority Priority MEDIUM 2 MEDIUM, 2 LOW
Other records, highest priority first
- TI-2020-12352 Use after free in Mozilla FirefoxPriority MEDIUM 42
- TI-2020-12351 Open redirect in Mozilla FirefoxPriority LOW 31
- TI-2020-12350 Cross-site scripting in Mozilla FirefoxPriority LOW 30
Show 2 more groups
- Advisory ·
Mozilla Firefox, Firefox ESR, Thunderbird — GLSA-202010-02
4 records Highest priority Priority MEDIUM 2 MEDIUM, 2 LOW
Other records, highest priority first
- TI-2020-12352 Use after free in Mozilla FirefoxPriority MEDIUM 42
- TI-2020-12351 Open redirect in Mozilla FirefoxPriority LOW 31
- TI-2020-12350 Cross-site scripting in Mozilla FirefoxPriority LOW 30
- Advisory ·
Mozilla Firefox, Firefox ESR, Thunderbird — DSA-4770
4 records Highest priority Priority MEDIUM 2 MEDIUM, 2 LOW
Other records, highest priority first
- TI-2020-12352 Use after free in Mozilla FirefoxPriority MEDIUM 42
- TI-2020-12351 Open redirect in Mozilla FirefoxPriority LOW 31
- TI-2020-12350 Cross-site scripting in Mozilla FirefoxPriority LOW 30
Vendor assessments
Red Hat
Red Hat rating: Important. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 5 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux AppStream (v. 8) | Fixed | RHSA-2020:3832, RHSA-2020:4155 |
| Red Hat Enterprise Linux AppStream E4S (v. 8.0) | Fixed | RHSA-2020:3834, RHSA-2020:4156 |
| Red Hat Enterprise Linux AppStream EUS (v. 8.1) | Fixed | RHSA-2020:3833, RHSA-2020:4157 |
| Red Hat Enterprise Linux Client (v. 7) | Fixed | RHSA-2020:4080, RHSA-2020:4163 |
| Red Hat Enterprise Linux Client Optional (v. 7) | Fixed | RHSA-2020:4080 |
| Red Hat Enterprise Linux Desktop (v. 6) | Fixed | RHSA-2020:3835, RHSA-2020:4158 |
| Red Hat Enterprise Linux Desktop Optional (v. 6) | Fixed | RHSA-2020:3835 |
| Red Hat Enterprise Linux HPC Node Optional (v. 6) | Fixed | RHSA-2020:3835 |
| Red Hat Enterprise Linux Server (v. 6) | Fixed | RHSA-2020:3835 |
| Red Hat Enterprise Linux Server (v. 7) | Fixed | RHSA-2020:4080 |
| Red Hat Enterprise Linux Server Optional (v. 6) | Fixed | RHSA-2020:3835, RHSA-2020:4158 |
| Red Hat Enterprise Linux Server Optional (v. 7) | Fixed | RHSA-2020:4080, RHSA-2020:4163 |
| Red Hat Enterprise Linux Workstation (v. 6) | Fixed | RHSA-2020:3835, RHSA-2020:4158 |
| Red Hat Enterprise Linux Workstation (v. 7) | Fixed | RHSA-2020:4080, RHSA-2020:4163 |
| Red Hat Enterprise Linux Workstation Optional (v. 6) | Fixed | RHSA-2020:3835 |
| Red Hat Enterprise Linux Workstation Optional (v. 7) | Fixed | RHSA-2020:4080 |
Timeline
- 2026-10-02 Threatist record created from CVE-2020-15673
- 2026-10-03 Alias added: GHSA-662r-59mf-5fxr
References
Advisory 9
- https://www.mozilla.org/security/advisories/mfsa2020-43/
- https://www.mozilla.org/security/advisories/mfsa2020-44/
- https://www.mozilla.org/security/advisories/mfsa2020-42/
- https://bugzilla.mozilla.org/buglist.cgi?bug_id=1648493%2C1660800
- DSA-4770
- [debian-lts-announce] 20201016 [SECURITY] [DLA 2408-1] thunderbird security update
- GLSA-202010-02
- openSUSE-SU-2020:1780
- openSUSE-SU-2020:1785
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-2020-15673 · CVE Program
- CVE-2020-15673 · NVD
- FIRST EPSS
- GHSA-662r-59mf-5fxr · GitHub Advisory Database · CC BY 4.0
- CVE-2020-15673 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences