medium 4.3

CVE-2025-5263 json

Error handling for script execution was incorrectly isolated from web content

published 2025-05-27 17 mo ago modified 2026-10-05 34 d ago also EUVD-2025-18108

cvss: 4.3; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 18%
public exploits: 0; none known

Error handling for script execution was incorrectly isolated from web content, which could have allowed cross-origin leak attacks. This vulnerability was fixed in Firefox 139, Firefox ESR 115.24, Firefox ESR 128.11, Thunderbird 139, and Thunderbird 128.11.

Patch / fix

fixed in 4 distros 7

mozilla firefox 115.24, 128.11, 139
mozilla firefox_esr 115.24, 128.11, 139
mozilla thunderbird 128.11, 139
mozilla thunderbird_esr 128.11, 139

debian ubuntu red hat suse opensuse almalinux rocky linux

firefox-esr Debian 12 128.11.0esr-1~deb12u1
firefox-esr Debian 14, Debian 13 128.11.0esr-1
thunderbird Debian 12 1:128.11.0esr-1~deb12u1
thunderbird Debian 14, Debian 13 1:128.11.0esr-1

debian advisories DEBIAN-CVE-2025-5263

thunderbird Ubuntu 22.04 LTS 1:128.12.0+build1-0ubuntu0.22.04.1

ubuntu advisories UBUNTU-CVE-2025-5263

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

thunderbird RHEL 8 128.11.0-1.el8_10
thunderbird RHEL 9 128.11.0-1.el9_6
thunderbird RHEL 10.0 128.11.0-1.el10_0
firefox RHEL 10.0 128.11.0-1.el10_0
firefox RHEL 8 128.11.0-1.el8_10
firefox RHEL 9 128.11.0-1.el9_6
firefox-x11 RHEL 9 128.11.0-1.el9_6
firefox RHEL 8.6 TUS, RHEL 8.6 E4S, RHEL 8.6 AUS 128.11.0-1.el8_6

red hat advisories RHSA-2025:9155 RHSA-2025:9077 RHSA-2025:9076 RHSA-2025:9074 RHSA-2025:9075 RHSA-2025:9073

mozjs128 SLES for SAP applications 16.0, SLES 16.0 128.14.0-160000.1.1
MozillaThunderbird SLE Workstation Extension 15 SP7, SLE Workstation Extension 15 SP6, SLE Module for Package Hub 15 SP7 +2 more 128.11.0-150200.8.221.1
MozillaFirefox SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES for SAP 15 SP3 +12 more 128.11.0-150200.152.185.1
MozillaFirefox SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 128.11.0-112.262.1

suse advisories SUSE-SU-2025:21170-1 SUSE-SU-2025:01946-1 SUSE-SU-2025:01814-1 SUSE-SU-2025:01769-1

mozjs128 openSUSE Leap 16.0 128.14.0-160000.1.1
mozjs128 openSUSE Tumbleweed 128.12.0-1.1
MozillaFirefox openSUSE Tumbleweed 139.0.1-1.1
MozillaThunderbird openSUSE Tumbleweed 128.11.0-1.1
firefox-esr openSUSE Tumbleweed 128.11.0-1.1

opensuse advisories openSUSE-SU-2025:20135-1 openSUSE-SU-2025:15315-1 openSUSE-SU-2025:15196-1 openSUSE-SU-2025:15174-1 openSUSE-SU-2025:15170-1

thunderbird AlmaLinux 8 128.11.0-1.el8_10.alma.1
thunderbird AlmaLinux 9 128.11.0-1.el9_6.alma.1
thunderbird AlmaLinux 10 128.11.0-1.el10_0.alma.1
firefox AlmaLinux 10 128.11.0-1.el10_0
firefox AlmaLinux 9 128.11.0-1.el9_6.alma.1
firefox-x11 AlmaLinux 9 128.11.0-1.el9_6.alma.1
firefox AlmaLinux 8 128.11.0-1.el8_10.alma.1

almalinux advisories ALSA-2025:8756 ALSA-2025:8607 ALSA-2025:8608 ALSA-2025:8341 ALSA-2025:8293 ALSA-2025:8308

firefox Rocky Linux 9 128.11.0-1.el9_6
thunderbird Rocky Linux 9 128.11.0-1.el9_6
firefox Rocky Linux 10 128.11.0-1.el10_0
thunderbird Rocky Linux 10 128.11.0-1.el10_0
firefox Rocky Linux 8 128.11.0-1.el8_10
thunderbird Rocky Linux 8 128.11.0-1.el8_10

rocky linux advisories RLSA-2025:8293 RLSA-2025:8607 RLSA-2025:8341 RLSA-2025:8608 RLSA-2025:8308 RLSA-2025:8756

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-5263 updated 2026-11-07 cvss 6.1

firefox: thunderbird: Error handling for script execution was incorrectly isolated from web content

Red Hat Enterprise Linux 6 firefox, thunderbird Red Hat Enterprise Linux 7 thunderbird
affected: no fix planned “Out of support scope”
Red Hat Enterprise Linux 10 firefox-flatpak, thunderbird-flatpak
affected: no fix available
Red Hat Enterprise Linux AppStream (v. 8) firefox 128.11.0-1.el8_10, thunderbird 128.11.0-1.el8_10
fixed: vendor fix RHSA-2025:8308
Red Hat Enterprise Linux AppStream (v. 9) firefox 128.11.0-1.el9_6, firefox-x11 128.11.0-1.el9_6, thunderbird 128.11.0-1.el9_6
fixed: vendor fix RHSA-2025:8293
Red Hat Enterprise Linux AppStream (v. 10) firefox 128.11.0-1.el10_0, thunderbird 128.11.0-1.el10_0
fixed: vendor fix RHSA-2025:8341
Red Hat Enterprise Linux AppStream AUS (v. 8.2) firefox 128.11.0-1.el8_2, thunderbird 128.11.0-1.el8_2
fixed: vendor fix RHSA-2025:9075
Red Hat Enterprise Linux AppStream AUS (v.8.4) firefox 128.11.0-1.el8_4, thunderbird 128.11.0-1.el8_4
fixed: vendor fix RHSA-2025:9076
Red Hat Enterprise Linux AppStream AUS (v.8.6) firefox 128.11.0-1.el8_6, thunderbird 128.11.0-1.el8_6 Red Hat Enterprise Linux AppStream E4S (v.8.6) firefox 128.11.0-1.el8_6, thunderbird 128.11.0-1.el8_6
fixed: vendor fix RHSA-2025:9155

show 7 more

Red Hat Enterprise Linux AppStream E4S (v.8.8) firefox 128.11.0-1.el8_8, thunderbird 128.11.0-1.el8_8
fixed: vendor fix RHSA-2025:9077
Red Hat Enterprise Linux AppStream E4S (v.9.0) firefox 128.11.0-1.el9_0, thunderbird 128.11.0-1.el9_0
fixed: vendor fix RHSA-2025:9073
Red Hat Enterprise Linux AppStream E4S (v.9.2) firefox 128.11.0-1.el9_2, firefox-x11 128.11.0-1.el9_2, thunderbird 128.11.0-1.el9_2
fixed: vendor fix RHSA-2025:9071
Red Hat Enterprise Linux AppStream EUS (v.9.4) firefox 128.11.0-1.el9_4, firefox-x11 128.11.0-1.el9_4, thunderbird 128.11.0-1.el9_4
fixed: vendor fix RHSA-2025:9072
Red Hat Enterprise Linux AppStream TUS (v.8.6) firefox 128.11.0-1.el8_6, thunderbird 128.11.0-1.el8_6
fixed: vendor fix RHSA-2025:9155
Red Hat Enterprise Linux AppStream TUS (v.8.8) thunderbird 128.11.0-1.el8_8
fixed: vendor fix RHSA-2025:8628
Red Hat Enterprise Linux Server (v. 7 ELS) firefox 128.11.0-1.el7_9
fixed: vendor fix RHSA-2025:9074

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 17 mo ago (2025-05-27)

Exploit prediction

0.27% chance of exploitation in the next 30 days, higher than 18% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CISA ADP	3.1	4.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
CNA	3.1	4.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

Affected products

Mozilla Firefox
Mozilla Thunderbird

Classification

Weakness

CWE-346 Origin Validation Error

References

mozilla.org /security/advisories/mfsa2025-42/
vendor-advisory
mozilla.org /security/advisories/mfsa2025-43/
vendor-advisory
mozilla.org /security/advisories/mfsa2025-44/
vendor-advisory
bugzilla.mozilla.org /show_bug.cgi?id=1960745
permissions-required
mozilla.org /security/advisories/mfsa2025-45/
mozilla.org /security/advisories/mfsa2025-46/
lists.debian.org /debian-lts-announce/2025/05/msg00046.html
lists.debian.org /debian-lts-announce/2025/05/msg00043.html

Sources

CVE List CVE-2025-5263
NVD CVE-2025-5263

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary