CVE-2026-16353: Invalid pointer in the DOM: Bindings (WebIDL) component

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CRITICAL 9.8REMOTEUPGRADEUPGRADE

CVE-2026-16353 is a critical-severity flaw (CVSS 9.8) affecting firefox, thunderbird. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Invalid pointer in the DOM: Bindings (WebIDL) component. This vulnerability was fixed in Firefox 153, Firefox ESR 115.38, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.

Why this priority

Critical severity
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 57%)
CISA exploited list	No
Weakness	CWE-416, CWE-476, CWE-824
Published	2026-07-21
Last modified	2026-10-24

Publisher (CNA): Mozilla Corporation · Vendor: mozilla

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-21 13:17 UTCPublished CVE record published
2026-10-24 20:10 UTCUpdated Record last modified

mozilla firefox UPGRADE

Affected: < 115.38.0 · < 153.0.0 · >= 128.1.0 and < 140.13.0

Fixed in: 115.38.0, 140.13.0, 153.0.0

Safe to downgrade to: a release before 128.1.0

1. Check installed version

apt-cache policy firefox || rpm -q firefox || firefox --version

2. UPGRADE to 115.38.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade firefox

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade firefox

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 128.1.0 (Debian / Ubuntu)

apt-cache madison firefox sudo apt install firefox=<VERSION_BEFORE_128.1.0> sudo apt-mark hold firefox

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list firefox sudo dnf downgrade firefox-<VERSION_BEFORE_128.1.0> sudo dnf versionlock add firefox

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

mozilla thunderbird UPGRADE

Affected: < 140.13.0 · >= 141.0 and < 153.0

Fixed in: 140.13.0, 153.0

Safe to downgrade to: a release before 141.0

1. Check installed version

apt-cache policy thunderbird || rpm -q thunderbird || thunderbird --version

2. UPGRADE to 140.13.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade thunderbird

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade thunderbird

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 141.0 (Debian / Ubuntu)

apt-cache madison thunderbird sudo apt install thunderbird=<VERSION_BEFORE_141.0> sudo apt-mark hold thunderbird

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list thunderbird sudo dnf downgrade thunderbird-<VERSION_BEFORE_141.0> sudo dnf versionlock add thunderbird

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Exact fixes by distribution

Fedora 46 · perl-Alien-Brotli · FIXED · 0.2.2-16.fc46 · FEDORA-2026-a2abe3db79 · source

sudo dnf upgrade --advisory=FEDORA-2026-a2abe3db79

Fedora ELN · mariadb-connector-odbc · FIXED · 3.2.10-1.eln159 · FEDORA-2026-b481dcd597 · source

sudo dnf upgrade --advisory=FEDORA-2026-b481dcd597

Ubuntu 22.04 · firefox · NOT AFFECTED

Ubuntu 24.04 · firefox · NOT AFFECTED

Ubuntu 22.04 · thunderbird · NO FIX YET

Ubuntu 24.04 · thunderbird · NOT AFFECTED

Debian 12 · firefox-esr · FIXED · 140.13.0esr-1~deb12u1

sudo apt update && sudo apt install --only-upgrade firefox-esr dpkg --compare-versions "$(dpkg-query -W -f='${Version}' firefox-esr)" ge "140.13.0esr-1~deb12u1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · firefox-esr · FIXED · 140.13.0esr-1~deb13u1

sudo apt update && sudo apt install --only-upgrade firefox-esr dpkg --compare-versions "$(dpkg-query -W -f='${Version}' firefox-esr)" ge "140.13.0esr-1~deb13u1" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · thunderbird · FIXED · 1:140.13.0esr-2~deb12u1

sudo apt update && sudo apt install --only-upgrade thunderbird dpkg --compare-versions "$(dpkg-query -W -f='${Version}' thunderbird)" ge "1:140.13.0esr-2~deb12u1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · thunderbird · FIXED · 1:140.13.0esr-2~deb13u1

sudo apt update && sudo apt install --only-upgrade thunderbird dpkg --compare-versions "$(dpkg-query -W -f='${Version}' thunderbird)" ge "1:140.13.0esr-2~deb13u1" && echo PATCHED || echo STILL-VULNERABLE

RHEL 10 · firefox · FIXED · firefox-140.13.0-1.el10_2

sudo dnf upgrade --advisory=RHSA-2026:47101 rpm -q firefox

RHEL 10 · thunderbird · FIXED · thunderbird-140.13.0-1.el10_2

sudo dnf upgrade --advisory=RHSA-2026:49621 rpm -q thunderbird

RHEL 10.0 Extended Update Support · thunderbird · FIXED · thunderbird-140.13.0-1.el10_0

sudo dnf upgrade --advisory=RHSA-2026:53445 rpm -q thunderbird

RHEL 10.0 Extended Update Support · firefox · FIXED · firefox-140.13.0-1.el10_0

sudo dnf upgrade --advisory=RHSA-2026:54181 rpm -q firefox

RHEL 7 Extended Lifecycle Support · firefox · FIXED · firefox-140.13.0-1.el7_9

sudo dnf upgrade --advisory=RHSA-2026:54248 rpm -q firefox

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2026-2069 · source

sudo dnf update --advisory=ALAS2023-2026-2069

Advisories and coverage

Official advisories

Amazon Linux 2 ALAS: ALAS2FIREFOX-2026-063 (important): firefox 2026-08-17

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-16353?

firefox: upgrade to 115.38.0, 140.13.0, 153.0.0; thunderbird: upgrade to 140.13.0, 153.0. Exact commands for each OS are on this page.

Is CVE-2026-16353 being exploited?

CVE-2026-16353 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-16353 affect?

CVE-2026-16353 affects firefox, thunderbird. Severity is critical (CVSS 9.8). Invalid pointer in the DOM: Bindings (WebIDL) component. This vulnerability was fixed in Firefox 153, Firefox ESR 115.38, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.

How urgent is CVE-2026-16353?

Priority 53/100. Critical severity; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Software pages

Mozilla Firefox vulnerabilities · Mozilla Thunderbird vulnerabilities

Related CVEs

CVE-2026-16389 CRITICAL 9.8 UPGRADE UPGRADE Incorrect boundary conditions, integer overflow in the Libraries component in NSS
CVE-2026-16360 CRITICAL 9.8 UPGRADE UPGRADE Memory safety bugs present in Thunderbird ESR 140.12 and Thunderbird 152
CVE-2026-16363 CRITICAL 9.8 UPGRADE UPGRADE JIT miscompilation in the JavaScript: WebAssembly component
CVE-2026-16369 CRITICAL 9.8 UPGRADE UPGRADE Integer overflow in the JavaScript: WebAssembly component
CVE-2026-16408 CRITICAL 9.8 UPGRADE Integer overflow in the Audio/Video: Playback component

References

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