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CVE-2026-4729

Memory safety bugs fixed in Firefox 149 and Thunderbird 149

9.8 Critical

Memory safety bugs present in Firefox 148 and Thunderbird 148. 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 was fixed in Firefox 149 and Thunderbird 149.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

0.35%Up 0.3 points since Mar 25, 2026
90%50%10%1%

What each source reports

CVE List Score used 9.8

Memory safety bugs fixed in Firefox 149 and Thunderbird 149

Memory safety bugs present in Firefox 148 and Thunderbird 148. 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 was fixed in Firefox 149 and Thunderbird 149.

Record
CVE-2026-4729
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness
CWE-120, CWE-825
Updated
2026-11-02
EUVDEUVD-2026-14873 9.8

Memory safety bugs present in Firefox 148 and Thunderbird 148. 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 was fixed in Firefox 149 and Thunderbird 149.

Record
EUVD-2026-14873
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
GitHub AdvisoriesGHSA-xh4v-qr89-3hj3 9.8

Memory safety bugs present in Firefox 148 and Thunderbird 148. Some of these bugs showed evidence...

Memory safety bugs present in Firefox 148 and Thunderbird 148. 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 < 149.

Record
GHSA-xh4v-qr89-3hj3
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-120, CWE-825
Updated
2026-11-02
NVD 9.8

Memory safety bugs present in Firefox 148 and Thunderbird 148. 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 was fixed in Firefox 149 and Thunderbird 149.

Record
CVE-2026-4729
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness
CWE-120, CWE-825
Updated
2026-11-02
OSVUBUNTU-CVE-2026-4729 9.8

Memory safety bugs present in Firefox 148 and Thunderbird 148. 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 was fixed in Firefox 149 and Thunderbird 149.

Record
UBUNTU-CVE-2026-4729
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVopenSUSE-SU-2026:10458-1 No score

MozillaFirefox-149.0-1.1 on GA media

These are all security issues fixed in the MozillaFirefox-149.0-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2026:10458-1
Updated
2026-11-02
OSVopenSUSE-SU-2026:11373-1 No score

firefox-esr-153.0-1.1 on GA media

These are all security issues fixed in the firefox-esr-153.0-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2026:11373-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
mozjs52
Ubuntu:18.04:LTS
 All versions, plus listed versions
52.3.1-0ubuntu352.3.1-7fakesync152.8.1-0ubuntu0.18.04.152.9.1-0ubuntu0.18.04.1
 None known
mozjs38
Ubuntu:18.04:LTS
 All versions, plus listed versions
38.8.0~repack1-0ubuntu138.8.0~repack1-0ubuntu338.8.0~repack1-0ubuntu4
 None known
mozjs68
Ubuntu:20.04:LTS
 All versions, plus listed versions
68.5.0-1~fakesync68.5.0-2~fakesync68.6.0-168.6.0-1ubuntu1
 None known
mozjs52
Ubuntu:20.04:LTS
 All versions, plus listed versions
52.9.1-1build152.9.1-1ubuntu3
 None known
mozjs102
Ubuntu:22.04:LTS
 All versions, plus listed versions
102.11.0-0ubuntu0.22.04.1102.12.0-0ubuntu0.22.04.1102.13.0-0ubuntu0.22.04.1102.15.1-0ubuntu0.22.04.1
 None known
mozjs78
Ubuntu:22.04:LTS
 All versions, plus listed versions
78.13.0-178.15.0-278.15.0-4ubuntu1
 None known
mozjs91
Ubuntu:22.04:LTS
 All versions, plus listed versions
91.5.1-0ubuntu191.6.0-191.6.0-291.7.0-291.10.0-0ubuntu1
 None known
thunderbird
Ubuntu:22.04:LTS
 All versions, plus listed versions
1:91.1.2+build1-0ubuntu11:91.3.0+build2-0ubuntu11:91.3.1+build1-0ubuntu11:91.3.2+build1-0ubuntu11:91.4.0+build1.1-0ubuntu1
Show 34 moreShow less
1:91.4.0+build2-0ubuntu11:91.5.0+build1-0ubuntu11:91.5.1+build1-0ubuntu11:91.6.1+build1-0ubuntu11:91.7.0+build1-0ubuntu11:91.7.0+build2-0ubuntu11:91.8.0+build2-0ubuntu11:91.9.1+build1-0ubuntu0.22.04.11:91.11.0+build2-0ubuntu0.22.04.11:102.2.2+build1-0ubuntu0.22.04.11:102.4.2+build2-0ubuntu0.22.04.11:102.7.1+build2-0ubuntu0.22.04.11:102.8.0+build2-0ubuntu0.22.04.11:102.9.0+build1-0ubuntu0.22.04.11:102.10.0+build2-0ubuntu0.22.04.11:102.11.0+build1-0ubuntu0.22.04.11:102.13.0+build1-0ubuntu0.22.04.11:102.15.0+build1-0ubuntu0.22.04.11:102.15.1+build1-0ubuntu0.22.04.11:115.3.1+build1-0ubuntu0.22.04.21:115.4.1+build1-0ubuntu0.22.04.11:115.5.0+build1-0ubuntu0.22.04.11:115.6.0+build2-0ubuntu0.22.04.11:115.8.1+build1-0ubuntu0.22.04.11:115.9.0+build1-0ubuntu0.22.04.11:115.10.1+build1-0ubuntu0.22.04.11:115.11.0+build2-0ubuntu0.22.04.11:115.12.0+build3-0ubuntu0.22.04.11:115.13.0+build5-0ubuntu0.22.04.11:115.15.0+build1-0ubuntu0.22.04.11:115.16.0+build2-0ubuntu0.22.04.11:115.18.0+build1-0ubuntu0.22.04.11:128.12.0+build1-0ubuntu0.22.04.11:140.7.1+build1-0ubuntu0.22.04.1
 None known
mozjs102
Ubuntu:24.04:LTS
 All versions, plus listed versions
102.15.1-1102.15.1-3ubuntu2
 None known
mozjs115
Ubuntu:24.04:LTS
 All versions, plus listed versions
115.3.0-0ubuntu1115.4.0-2115.5.0-1115.6.0-1115.7.0-4
Show 4 moreShow less
115.8.0-1115.9.0-1115.9.0-1build1115.10.0-1
 None known
MozillaFirefox
openSUSE:Tumbleweed
From an advisory covering 46 CVEs
 before 149.0-1.1
149.0-1.1
firefox-esr
openSUSE:Tumbleweed
From an advisory covering 228 CVEs
 before 153.0-1.1
153.0-1.1

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-4729 is a critical vulnerability (CVSS 9.8) in Mozilla Firefox, published March 24, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.35%, the 29th percentile. No source names a fixed version.

References

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Left out here: 77 references. The JSON record has them.

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