HOMEVULNERABILITIESCVE-2026-4721
CRITICAL

CVE-2026-4721

Published: March 24, 2026· Updated: Mar 25, 2026

9.8
CVSS v3.1
EPSS:0.01%probability of exploitation in 30 daysPercentile:0.7th

Official Description

Memory safety bugs present in Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird ESR 140.8, 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, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.

NVD Source

Technical Analysis

CVE-2026-4721 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Vendors & Products

Mozilla2 products
firefoxthunderbird
Source: NVD CPE · 2 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

ADVISORYhttps://www.mozilla.org/security/advisories/mfsa2026-20/
ADVISORYhttps://www.mozilla.org/security/advisories/mfsa2026-21/
ADVISORYhttps://www.mozilla.org/security/advisories/mfsa2026-22/
ADVISORYhttps://www.mozilla.org/security/advisories/mfsa2026-23/
ADVISORYhttps://www.mozilla.org/security/advisories/mfsa2026-24/

All References (6)

→
https://bugzilla.mozilla.org/buglist.cgi?bug_id=2013762%2C2015291%2C2016591%2C2016661%2C2016664%2C2017303%2C2017894%2C2018090%2C2018196%2C2018379%2C2019112%2C2022090%2C2022243%2C2022351%2C2022478%2C2022676Broken Link
→
https://www.mozilla.org/security/advisories/mfsa2026-20/Vendor Advisory
→
https://www.mozilla.org/security/advisories/mfsa2026-21/Vendor Advisory
→
https://www.mozilla.org/security/advisories/mfsa2026-22/Vendor Advisory
→
https://www.mozilla.org/security/advisories/mfsa2026-23/Vendor Advisory
→
https://www.mozilla.org/security/advisories/mfsa2026-24/Vendor Advisory

Quick Facts

CVE IDCVE-2026-4721
CVSS Score9.8 / 10
SeverityCRITICAL
CISA KEVNo
EPSS (30d)0.01%
Affected1 vendor
PublishedMar 24, 2026

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2026-4721 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.
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