CVE-2025-1936 [High] | Security Vulnerability in Firefox

jar: URLs retrieve local file content packaged in a ZIP archive. The null and everything after it was ignored when retrieving the content from the archive, but the fake extension after the null was used to determine the type of content. This could have been used to hide code in a web extension disguised as something else like an image. This vulnerability was fixed in Firefox 136, Firefox ESR 128.8, Thunderbird 136, and Thunderbird 128.8.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-04-12	0.48%	0.15%	-0.33%
2	2026-03-02	0.73%	0.48%	-0.25%
3	2025-12-29	—	0.73%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-04-12

0.48%

0.15%

-0.33%

2026-03-02

0.73%

0.48%

-0.25%

2025-12-29

—

0.73%

—

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-2025-1936

vendor	priority	summary	link
`alpine`	—	CVE-2025-1936: 3 source package rows (firefox, firefox-esr, thunderbird); 342 state rows across 2 repos (3.22-community, edge-community); fixed 0, open 342.	https://security.alpinelinux.org/vuln/CVE-2025-1936
`debian`	not yet assigned	CVE-2025-1936 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-2025-1936
`gentoo`	high	CVE-2025-1936: 3 GLSA(s) (202505-02, 202505-03, 202505-08), 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-2025-1936
`redhat`	low	—	https://access.redhat.com/security/cve/CVE-2025-1936
`suse`	high	CVE-2025-1936 severity important: SUSE including 35 source package names (MozillaFirefox-128.8.0-112.249.3, MozillaFirefox-128.8.0-150200.152.173.1, …), 137 product×package rows across 48 product lines (Container suse/kiosk/firefox-esr, Image SLES12-SP5-SAP-Azure-LI-BYOS-Production, … (48 product lines)): Fixed 137.	https://www.suse.com/security/cve/CVE-2025-1936/
`ubuntu`	medium	CVE-2025-1936 medium priority: Ubuntu including 9 source packages (firefox, mozjs102, …), 65 status rows across 8 suites (bionic, focal, jammy, noble, oracular, plucky, questing, upstream): DNE 34, ignored 10, needs-triage 9, not-affected 9, released 3.	https://ubuntu.com/security/CVE-2025-1936

Affected software / configurations for CVE-2025-1936

Vendor	Product	Version	Raw CPE
mozilla	firefox	< 128.8.0	cpe:2.3:a:mozilla:firefox:::::esr:::*
mozilla	firefox	< 136.0	cpe:2.3:a:mozilla:firefox:::::-:::*
mozilla	thunderbird	< 128.8.0	cpe:2.3:a:mozilla:thunderbird::::::::
mozilla	thunderbird	>= 129.0, < 136.0	cpe:2.3:a:mozilla:thunderbird::::::::

References for CVE-2025-1936

URL	Tags
https://bugzilla.mozilla.org/show_bug.cgi?id=1940027	Permissions Required
https://www.mozilla.org/security/advisories/mfsa2025-14/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-16/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-17/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-18/	Vendor Advisory
https://lists.debian.org/debian-lts-announce/2025/03/msg00006.html

URL

CVE-2025-1936 | Adding %00 and a fake extension to a jar: URL changed the interpretation of the contents

Exploit prediction scoring system (EPSS) score for CVE-2025-1936

Common vulnerability scoring system (CVSS) metrics for CVE-2025-1936

Weakness enumeration for CVE-2025-1936

OS Trackers for CVE-2025-1936

Affected software / configurations for CVE-2025-1936

References for CVE-2025-1936