CVE-2025-0239

14

FAUCET Score

CVE-2025-0239 describes a certificate validation flaw in Mozilla Firefox and Thunderbird versions prior to 134/128.6 respectively. When using Alt-Svc, the affected applications failed to properly validate certificates when an original server redirected to an insecure site. This vulnerability has a CVSS score of 4.0 (Medium), indicating a low attack complexity and impact limited to integrity, with no confidentiality or availability impact. There is currently no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

Vendor	Product	Version(s)	CPE
		< 128.6.0CPE matchmatch criteria	cpe:2.3:a:mozilla:firefox:::::esr:::*
		< 134.0CPE matchmatch criteria	cpe:2.3:a:mozilla:firefox::::::::
		< 128.6.0CPE matchmatch criteria	cpe:2.3:a:mozilla:thunderbird::::::::
		>= 129.0, < 134.0CPE matchmatch criteria	cpe:2.3:a:mozilla:thunderbird::::::::

CVSS Data

CVSS version used by this source: 3.1

4.0MEDIUM

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

LOW

Availability Impact

NONE

Exploitability Score

2.5

Impact Score

1.4

CvssVersion

3.1

Exploit Intelligence

EPSS Score

0.23%

Probability of exploitation in next 30 days

EPSS Percentile

13.5%

Percentile rank of EPSS score among Peer Group

As of 2026-07-28

Model: v2026.06.15

This CVE's current EPSS score of 0.0023 is in the 23rd percentile among its peer group of 3,052 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (34)

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 7 Extended Lifecycle SupportFixed in: firefox-0:128.6.0-1.el7_9

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8Fixed in: firefox-0:128.6.0-1.el8_10

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8Fixed in: thunderbird-0:128.6.0-3.el8_10

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.2 Advanced Update SupportFixed in: firefox-0:128.6.0-1.el8_2

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.2 Advanced Update SupportFixed in: thunderbird-0:128.6.0-3.el8_2

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update SupportFixed in: firefox-0:128.6.0-1.el8_4

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update SupportFixed in: thunderbird-0:128.6.0-3.el8_4

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.4 Telecommunications Update ServiceFixed in: firefox-0:128.6.0-1.el8_4

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.4 Telecommunications Update ServiceFixed in: thunderbird-0:128.6.0-3.el8_4

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.4 Update Services for SAP SolutionsFixed in: firefox-0:128.6.0-1.el8_4

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.4 Update Services for SAP SolutionsFixed in: thunderbird-0:128.6.0-3.el8_4

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update SupportFixed in: firefox-0:128.6.0-1.el8_6

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update SupportFixed in: thunderbird-0:128.6.0-3.el8_6

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.6 Telecommunications Update ServiceFixed in: firefox-0:128.6.0-1.el8_6

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.6 Telecommunications Update ServiceFixed in: thunderbird-0:128.6.0-3.el8_6

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.6 Update Services for SAP SolutionsFixed in: firefox-0:128.6.0-1.el8_6

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.6 Update Services for SAP SolutionsFixed in: thunderbird-0:128.6.0-3.el8_6

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.8 Extended Update SupportFixed in: firefox-0:128.6.0-1.el8_8

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.8 Extended Update SupportFixed in: thunderbird-0:128.6.0-3.el8_8

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 9Fixed in: firefox-0:128.6.0-1.el9_5

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 9Fixed in: thunderbird-0:128.6.0-3.el9_5

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 9.0 Update Services for SAP SolutionsFixed in: firefox-0:128.6.0-1.el9_0

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 9.0 Update Services for SAP SolutionsFixed in: thunderbird-0:128.6.0-3.el9_0

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 9.2 Extended Update SupportFixed in: firefox-0:128.6.0-1.el9_2

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 9.2 Extended Update SupportFixed in: thunderbird-0:128.6.0-3.el9_2

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 9.4 Extended Update SupportFixed in: firefox-0:128.6.0-1.el9_4

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 9.4 Extended Update SupportFixed in: thunderbird-0:128.6.0-3.el9_4

mozillavendor investigatingvia nvd_reference

redhatno patchvia redhat_api

Product: Red Hat Enterprise Linux 10Fixed in: firefox-flatpak-container

redhatno patchvia redhat_api

Product: Red Hat Enterprise Linux 10Fixed in: thunderbird

redhatno patchvia redhat_api

Product: Red Hat Enterprise Linux 10Fixed in: firefox

redhatno patchvia redhat_api

Product: Red Hat Enterprise Linux 9Fixed in: firefox:flatpak/firefox

redhatno patchvia redhat_api

Product: Red Hat Enterprise Linux 9Fixed in: thunderbird:flatpak/thunderbird

redhatno patchvia redhat_api

Product: Red Hat Enterprise Linux 10Fixed in: thunderbird-flatpak-container

Vendor Advisories (1)

redhatCVE-2025-0239Moderate

firefox: Alt-Svc ALPN validation failure when redirected

References

lists.debian.org / debian-lts-announce/2025/01/msg00004.html

bugzilla.mozilla.org / show_bug.cgi

Issue TrackingPermissions Required

mozilla.org / security/advisories/mfsa2025-01

Vendor Advisory

mozilla.org / security/advisories/mfsa2025-02

Vendor Advisory

mozilla.org / security/advisories/mfsa2025-04

Vendor Advisory

mozilla.org / security/advisories/mfsa2025-05

Vendor Advisory