CVE-2026-2781 [Critical] | Integer Overflow in Firefox

CVE-2026-2781 is rated Moderate Risk (44.7/100): CVSS Critical severity, with low exploitation likelihood (EPSS 0.05%). Review affected assets and schedule remediation.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-03-28	0.02%	0.05%	+0.03%
2	2026-02-25	—	0.02%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-03-28

0.02%

0.05%

+0.03%

2026-02-25

—

0.02%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
9.8	3.1	CRITICAL	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	3.9	5.9	[email protected]
8.8	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:R) A real person has to do something—click, install, enable—otherwise it doesn’t land. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	2.8	5.9	134c704f-9b21-4f2e-91b3-4a467353bcc0

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

9.8

3.1

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H): Serious risk that confidential data gets exposed in a big way.
Integrity (I:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

3.9

5.9

[email protected]

8.8

3.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R): A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H): Serious risk that confidential data gets exposed in a big way.
Integrity (I:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

2.8

5.9

134c704f-9b21-4f2e-91b3-4a467353bcc0

OS Trackers for CVE-2026-2781

vendor	priority	summary	link
`alpine`	—	CVE-2026-2781: 2 source package rows (firefox, thunderbird); 179 state rows across 2 repos (3.23-community, edge-community); fixed 0, open 179.	https://security.alpinelinux.org/vuln/CVE-2026-2781
`debian`	not yet assigned	CVE-2026-2781 not yet assigned priority: Debian including 4 source packages (firefox, firefox-esr, nss, thunderbird), 16 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 16.	https://security-tracker.debian.org/tracker/CVE-2026-2781
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2026-2781
`suse`	high	CVE-2026-2781 severity important: SUSE including 87 source package names (13.2-9.16:rpm-4.18.0-7.1, 2.0.4-3.5.476:libfreebl3-3.112.3-150400.3.63.1, …), 544 product×package rows across 87 product lines (Container suse/manager/5.0/x86_64/server, Container suse/manager/5.0/x86_64/server-attestation, … (87 product lines)): Fixed 540, First Fixed 4.	https://www.suse.com/security/cve/CVE-2026-2781/
`ubuntu`	medium	CVE-2026-2781 medium priority: Ubuntu including 3 source packages (firefox, nss, thunderbird), 19 status rows across 9 suites (bionic, focal, jammy, noble, questing, resolute, trusty, upstream, xenial): released 10, not-affected 7, needed 1, needs-triage 1.	https://ubuntu.com/security/CVE-2026-2781

Affected software / configurations for CVE-2026-2781

Vendor	Product	Version	Raw CPE
mozilla	firefox	< 140.8.0	cpe:2.3:a:mozilla:firefox:::::esr:::*
mozilla	firefox	< 148.0	cpe:2.3:a:mozilla:firefox:::::-:::*
mozilla	thunderbird	< 140.8.0	cpe:2.3:a:mozilla:thunderbird:::::esr:::*
mozilla	thunderbird	< 148.0	cpe:2.3:a:mozilla:thunderbird:::::-:::*

References for CVE-2026-2781

URL	Tags
https://bugzilla.mozilla.org/show_bug.cgi?id=2009552	Issue Tracking Permissions Required
https://www.mozilla.org/security/advisories/mfsa2026-13/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-15/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-16/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-17/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-31/
https://lists.debian.org/debian-lts-announce/2026/03/msg00012.html

URL

CVE-2026-2781 | Integer overflow in the Libraries component in NSS

Exploit prediction scoring system (EPSS) score for CVE-2026-2781

Common vulnerability scoring system (CVSS) metrics for CVE-2026-2781

Weakness enumeration for CVE-2026-2781

GitHub Security Advisory for CVE-2026-2781

OS Trackers for CVE-2026-2781

Affected software / configurations for CVE-2026-2781

References for CVE-2026-2781