CVE-2025-2817 [High] | Path Traversal in Firefox

Thunderbird's update mechanism allowed a medium-integrity user process to interfere with the SYSTEM-level updater by manipulating the file-locking behavior. By injecting code into the user-privileged process, an attacker could bypass intended access controls, allowing SYSTEM-level file operations on paths controlled by a non-privileged user and enabling privilege escalation. This vulnerability was fixed in Firefox 138, Firefox ESR 128.10, Firefox ESR 115.23, Thunderbird 138, and Thunderbird 128.10.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-07	0.19%	0.12%	-0.07%
2	2026-05-25	0.38%	0.19%	-0.19%
3	2026-02-23	—	0.38%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-07

0.19%

0.12%

-0.07%

2026-05-25

0.38%

0.19%

-0.19%

2026-02-23

—

0.38%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
8.8	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:L/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:L) A normal user session is enough; they don’t have to be admin. 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.	2.8	5.9	134c704f-9b21-4f2e-91b3-4a467353bcc0

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

8.8

3.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:L/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:L): A normal user session is enough; they don’t have to be admin.
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.

2.8

5.9

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

OS Trackers for CVE-2025-2817

vendor	priority	summary	link
`alpine`	—	CVE-2025-2817: 3 source package rows (firefox, firefox-esr, thunderbird); 353 state rows across 2 repos (3.22-community, edge-community); fixed 0, open 353.	https://security.alpinelinux.org/vuln/CVE-2025-2817
`debian`	unimportant	CVE-2025-2817 unimportant 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-2025-2817
`redhat`	high	—	https://access.redhat.com/security/cve/CVE-2025-2817
`suse`	high	CVE-2025-2817 severity important: SUSE including 34 source package names (MozillaFirefox-128.10.0-112.255.1, MozillaFirefox-128.10.0-150200.152.179.1, …), 124 product×package rows across 44 product lines (Container suse/kiosk/firefox-esr, Image SLES12-SP5-SAP-Azure-LI-BYOS-Production, … (44 product lines)): Fixed 124.	https://www.suse.com/security/cve/CVE-2025-2817/
`ubuntu`	medium	CVE-2025-2817 medium priority: Ubuntu including 2 source packages (firefox, thunderbird), 12 status rows across 6 suites (focal, jammy, noble, oracular, plucky, upstream): not-affected 9, DNE 2, released 1.	https://ubuntu.com/security/CVE-2025-2817

Affected software / configurations for CVE-2025-2817

Vendor	Product	Version	Raw CPE
mozilla	firefox	< 115.23.0	cpe:2.3:a:mozilla:firefox:::::esr:::*
mozilla	firefox	< 138.0	cpe:2.3:a:mozilla:firefox:::::-:::*
mozilla	firefox	>= 116.0, < 128.10.0	cpe:2.3:a:mozilla:firefox:::::esr:::*
mozilla	thunderbird	< 128.10.0	cpe:2.3:a:mozilla:thunderbird::::::::
mozilla	thunderbird	>= 129.0, < 138.0	cpe:2.3:a:mozilla:thunderbird::::::::

References for CVE-2025-2817

URL	Tags
https://bugzilla.mozilla.org/show_bug.cgi?id=1917536	Permissions Required
https://www.mozilla.org/security/advisories/mfsa2025-28/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-29/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-30/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-31/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-32/	Vendor Advisory
https://lists.debian.org/debian-lts-announce/2025/05/msg00022.html

URL

CVE-2025-2817 | Privilege escalation in Thunderbird Updater

Exploit prediction scoring system (EPSS) score for CVE-2025-2817

Common vulnerability scoring system (CVSS) metrics for CVE-2025-2817

Weakness enumeration for CVE-2025-2817

OS Trackers for CVE-2025-2817

Affected software / configurations for CVE-2025-2817

References for CVE-2025-2817