CVE-2025-3029 [High] | Spoofing in Firefox

A crafted URL containing specific Unicode characters could have hidden the true origin of the page, resulting in a potential spoofing attack. This vulnerability was fixed in Firefox 137, Firefox ESR 128.9, Thunderbird 137, and Thunderbird 128.9.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-05-10	0.65%	0.13%	-0.52%
2	2026-01-26	0.16%	0.65%	+0.49%
3	2025-12-16	—	0.16%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-05-10

0.65%

0.13%

-0.52%

2026-01-26

0.16%

0.65%

+0.49%

2025-12-16

—

0.16%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.3	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L` 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:L) Some sensitive info could get out, but not a total data dump. Integrity (I:L) Attackers could change some data, but it’s limited—not everything goes. Availability (A:L) Might cause slowdowns, glitches, or partial disruption—not a full brick.	3.9	3.4	134c704f-9b21-4f2e-91b3-4a467353bcc0

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

7.3

3.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L 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:L): Some sensitive info could get out, but not a total data dump.
Integrity (I:L): Attackers could change some data, but it’s limited—not everything goes.
Availability (A:L): Might cause slowdowns, glitches, or partial disruption—not a full brick.

3.9

3.4

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

OS Trackers for CVE-2025-3029

vendor	priority	summary	link
`alpine`	—	CVE-2025-3029: 3 source package rows (firefox, firefox-esr, thunderbird); 349 state rows across 2 repos (3.22-community, edge-community); fixed 0, open 349.	https://security.alpinelinux.org/vuln/CVE-2025-3029
`debian`	not yet assigned	CVE-2025-3029 not yet assigned priority: Debian including 3 source packages (firefox, firefox-esr, thunderbird), 11 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 11.	https://security-tracker.debian.org/tracker/CVE-2025-3029
`gentoo`	high	CVE-2025-3029: 3 GLSA(s) (202505-02, 202505-03, 202509-02), 5 atom(s) (dev-lang/spidermonkey, mail-client/thunderbird, mail-client/thunderbird-bin, www-client/firefox, www-client/firefox-bin); latest impact high.	https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2025-3029
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2025-3029
`suse`	high	CVE-2025-3029 severity important: SUSE including 37 source package names (MozillaFirefox-128.9.0-112.252.1, MozillaFirefox-128.9.0-150200.152.176.1, …), 127 product×package rows across 44 product lines (Container suse/kiosk/firefox-esr, Image SLES12-SP5-SAP-Azure-LI-BYOS-Production, … (44 product lines)): Fixed 127.	https://www.suse.com/security/cve/CVE-2025-3029/
`ubuntu`	medium	CVE-2025-3029 medium priority: Ubuntu including 9 source packages (firefox, mozjs102, …), 65 status rows across 8 suites (bionic, focal, jammy, noble, oracular, plucky, questing, upstream): DNE 35, ignored 10, not-affected 9, needs-triage 8, released 3.	https://ubuntu.com/security/CVE-2025-3029

Affected software / configurations for CVE-2025-3029

Vendor	Product	Version	Raw CPE
mozilla	firefox	< 128.9.0	cpe:2.3:a:mozilla:firefox:::::esr:::*
mozilla	firefox	< 137.0	cpe:2.3:a:mozilla:firefox:::::-:::*
mozilla	thunderbird	< 128.9.0	cpe:2.3:a:mozilla:thunderbird::::::::
mozilla	thunderbird	>= 129.0, < 137.0	cpe:2.3:a:mozilla:thunderbird::::::::

References for CVE-2025-3029

URL	Tags
https://bugzilla.mozilla.org/show_bug.cgi?id=1952213	Issue Tracking Permissions Required
https://www.mozilla.org/security/advisories/mfsa2025-20/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-22/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-23/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-24/	Vendor Advisory
https://lists.debian.org/debian-lts-announce/2025/04/msg00005.html

URL

CVE-2025-3029 | URL Bar Spoofing via non-BMP Unicode characters

Exploit prediction scoring system (EPSS) score for CVE-2025-3029

Common vulnerability scoring system (CVSS) metrics for CVE-2025-3029

Weakness enumeration for CVE-2025-3029

OS Trackers for CVE-2025-3029

Affected software / configurations for CVE-2025-3029

References for CVE-2025-3029