critical 9.8

CVE-2025-4918 json

Out-of-bounds access when resolving Promise objects

published 2025-05-17 17 mo ago modified 2026-09-30 39 d ago also EUVD-2025-15599

cvss: 9.8; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 9.5%; EPSS 9.5% chance of exploitation in 30 days, percentile 95%
public exploits: 0; none known

An attacker was able to perform an out-of-bounds read or write on a JavaScript `Promise` object. This vulnerability was fixed in Firefox 138.0.4, Firefox ESR 128.10.1, Firefox ESR 115.23.1, Thunderbird 128.10.2, and Thunderbird 138.0.2.

Patch / fix

fixed in 4 distros 7

mozilla firefox 115.23.1, 128.10.1, 138.0.4
mozilla firefox_esr 115.23.1, 128.10.1, 138.0.4
mozilla thunderbird 128.10.1, 138.0.4
mozilla thunderbird_esr 128.10.1, 138.0.4

debian ubuntu red hat suse opensuse almalinux rocky linux

firefox-esr Debian 12 128.10.1esr-1~deb12u1
firefox-esr Debian 14, Debian 13 128.10.1esr-1
thunderbird Debian 12 1:128.11.0esr-1~deb12u1
thunderbird Debian 14, Debian 13 1:128.11.0esr-1

debian advisories DEBIAN-CVE-2025-4918

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

ubuntu advisories UBUNTU-CVE-2025-4918

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 10.0 128.10.1-1.el10_0
firefox RHEL 8 128.10.1-1.el8_10
firefox RHEL 9 128.10.1-1.el9_6
firefox-x11 RHEL 9 128.10.1-1.el9_6
firefox RHEL 8.8 TUS, RHEL 8.8 E4S 128.10.1-1.el8_8

red hat advisories RHSA-2025:8807 RHSA-2025:8756 RHSA-2025:8645 RHSA-2025:8640 RHSA-2025:8642 RHSA-2025:8639

MozillaThunderbird SLE Workstation Extension 15 SP7, SLE Workstation Extension 15 SP6, SLE Module for Package Hub 15 SP7 +2 more 128.10.2-150200.8.218.1
MozillaFirefox SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES for SAP 15 SP3 +11 more 128.10.1-150200.152.182.1
MozillaFirefox SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 128.10.1-112.259.1

suse advisories SUSE-SU-2025:01813-1 SUSE-SU-2025:01710-1 SUSE-SU-2025:01701-1

MozillaFirefox openSUSE Tumbleweed 138.0.4-1.1
MozillaThunderbird openSUSE Tumbleweed 128.10.2-1.1
firefox-esr openSUSE Tumbleweed 128.10.1-1.1

opensuse advisories openSUSE-SU-2025:15148-1 openSUSE-SU-2025:15149-1 openSUSE-SU-2025:15133-1

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 10 128.10.1-1.el10_0
firefox AlmaLinux 8 128.10.1-1.el8_10.alma.1
firefox AlmaLinux 9 128.10.1-1.el9_6.alma.1
firefox-x11 AlmaLinux 9 128.10.1-1.el9_6.alma.1

almalinux advisories ALSA-2025:8756 ALSA-2025:8607 ALSA-2025:8608 ALSA-2025:8125 ALSA-2025:8060 ALSA-2025:8049

thunderbird Rocky Linux 9 128.11.0-1.el9_6
firefox Rocky Linux 10 128.10.1-1.el10_0
thunderbird Rocky Linux 10 128.11.0-1.el10_0
firefox Rocky Linux 8 128.10.1-1.el8_10
thunderbird Rocky Linux 8 128.11.0-1.el8_10

rocky linux advisories RLSA-2025:8607 RLSA-2025:8125 RLSA-2025:8608 RLSA-2025:8060 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-2025-4918 updated 2026-11-04 cvss 8.8

firefox: thunderbird: Out-of-bounds access when resolving Promise objects

Red Hat Enterprise Linux 6 firefox, thunderbird Red Hat Enterprise Linux 7 thunderbird
affected: workaround, no fix planned “No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.”
Red Hat Enterprise Linux 10 firefox-flatpak, thunderbird-flatpak
affected: workaround, no fix available “No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.”
Red Hat Enterprise Linux AppStream (v. 8) firefox 128.10.1-1.el8_10, thunderbird 128.11.0-1.el8_10
fixed: vendor fix “No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.” RHSA-2025:8060
Red Hat Enterprise Linux AppStream (v. 9) firefox 128.10.1-1.el9_6, firefox-x11 128.10.1-1.el9_6, thunderbird 128.11.0-1.el9_6
fixed: vendor fix “No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.” RHSA-2025:8049
Red Hat Enterprise Linux AppStream (v. 10) firefox 128.10.1-1.el10_0, thunderbird 128.11.0-1.el10_0
fixed: vendor fix “No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.” RHSA-2025:8125
Red Hat Enterprise Linux AppStream AUS (v. 8.2) firefox 128.10.1-1.el8_2, thunderbird 128.11.0-1.el8_2
fixed: vendor fix “No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.” RHSA-2025:8639
Red Hat Enterprise Linux AppStream AUS (v.8.4) firefox 128.10.1-1.el8_4, thunderbird 128.11.0-1.el8_4
fixed: vendor fix “No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.” RHSA-2025:8640
Red Hat Enterprise Linux AppStream AUS (v.8.6) firefox 128.10.1-1.el8_6, thunderbird 128.11.0-1.el8_6 Red Hat Enterprise Linux AppStream E4S (v.8.6) firefox 128.10.1-1.el8_6, thunderbird 128.11.0-1.el8_6
fixed: vendor fix “No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.” RHSA-2025:8645

show 8 more

Red Hat Enterprise Linux AppStream E4S (v.8.8) firefox 128.10.1-1.el8_8, thunderbird 128.11.0-1.el8_8
fixed: vendor fix “No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.” RHSA-2025:8807
Red Hat Enterprise Linux AppStream E4S (v.9.0) firefox 128.10.1-1.el9_0, thunderbird 128.11.0-1.el9_0
fixed: vendor fix “No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.” RHSA-2025:8371
Red Hat Enterprise Linux AppStream E4S (v.9.2) thunderbird 128.11.0-1.el9_2
fixed: vendor fix “No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.” RHSA-2025:8642
Red Hat Enterprise Linux AppStream EUS (v.9.2) firefox 128.10.1-1.el9_2, firefox-x11 128.10.1-1.el9_2
fixed: vendor fix “No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.” RHSA-2025:8369
Red Hat Enterprise Linux AppStream EUS (v.9.4) firefox 128.10.1-1.el9_4, firefox-x11 128.10.1-1.el9_4, thunderbird 128.11.0-1.el9_4
fixed: vendor fix “No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.” RHSA-2025:8370
Red Hat Enterprise Linux AppStream TUS (v.8.6) firefox 128.10.1-1.el8_6, thunderbird 128.11.0-1.el8_6
fixed: vendor fix “No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.” RHSA-2025:8645
Red Hat Enterprise Linux AppStream TUS (v.8.8) firefox 128.10.1-1.el8_8, thunderbird 128.11.0-1.el8_8
fixed: vendor fix “No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.” RHSA-2025:8807
Red Hat Enterprise Linux Server (v. 7 ELS) firefox 128.10.1-1.el7_9
fixed: vendor fix “No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.” RHSA-2025:8465

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: total
Assessed: 17 mo ago (2025-05-20)

Exploit prediction

9.52% chance of exploitation in the next 30 days, higher than 95% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

vicarius.io https://www.vicarius.io/vsociety/posts/cve-2025-4918-detect-firefox-out-of-bounds-write referenced PoC, tagged "exploit" by a source, unverified
vicarius.io https://www.vicarius.io/vsociety/posts/cve-2025-4918-mitigate-firefox-out-of-bounds-write referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CISA ADP	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Mozilla Firefox
Mozilla Thunderbird

Classification

Weakness

CWE-125 Out-of-bounds Read
CWE-787 Out-of-bounds Write

References

vicarius.io /vsociety/posts/cve-2025-4918-detect-firefox-out-of-bounds-write
exploit, third-party-advisory
vicarius.io /vsociety/posts/cve-2025-4918-mitigate-firefox-out-of-bounds-write
exploit, third-party-advisory
mozilla.org /security/advisories/mfsa2025-36/
vendor-advisory
mozilla.org /security/advisories/mfsa2025-37/
vendor-advisory
mozilla.org /security/advisories/mfsa2025-38/
vendor-advisory
mozilla.org /security/advisories/mfsa2025-40/
vendor-advisory
mozilla.org /security/advisories/mfsa2025-41/
vendor-advisory
bugzilla.mozilla.org /show_bug.cgi?id=1966612
permissions-required
lists.debian.org /debian-lts-announce/2025/05/msg00046.html
lists.debian.org /debian-lts-announce/2025/05/msg00024.html

Sources

CVE List CVE-2025-4918
NVD CVE-2025-4918

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