CVE-2023-37207: A website could have obscured the fullscreen notification by using a URL with a scheme handled by an external

Q: How do I fix CVE-2023-37207?

firefox: upgrade to 115.0; firefox esr: upgrade to 102.13; thunderbird: upgrade to 102.13. Exact commands for each OS are on this page.

Q: Is CVE-2023-37207 being exploited?

CVE-2023-37207 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2023-37207 affect?

CVE-2023-37207 affects firefox, firefox esr, thunderbird. Severity is medium (CVSS 6.5). A website could have obscured the fullscreen notification by using a URL with a scheme handled by an external program, such as a mailto URL. This could have led to user confusion and possible spoofing attacks. This vulnerability affects Fir

Q: How urgent is CVE-2023-37207?

Priority 44/100. CISA SSVC: public proof of concept; On your watchlist

This month

MEDIUM 6.5WATCHLISTUPGRADEUPGRADEUPGRADE

CVE-2023-37207 is a medium-severity flaw (CVSS 6.5) affecting firefox, firefox esr, thunderbird. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A website could have obscured the fullscreen notification by using a URL with a scheme handled by an external program, such as a mailto URL. This could have led to user confusion and possible spoofing attacks. This vulnerability affects Firefox < 115, Firefox ESR < 102.13, and Thunderbird < 102.13.

Why this priority

CISA SSVC: public proof of concept
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.7% (top 46%)
CISA exploited list	No
Weakness	CWE-470
Published	2023-07-05
Last modified	2026-10-23

Publisher (CNA): Mozilla Corporation · Vendor: debian · mozilla

Am I affected?

Timeline

2023-07-05 09:15 UTCPublished CVE record published
2026-10-23 23:10 UTCUpdated Record last modified

mozilla firefox UPGRADE

Affected: < 115.0

Fixed in: 115.0

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 115.0 (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.

mozilla firefox esr UPGRADE

Affected: < 102.13

Fixed in: 102.13

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 102.13 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade firefox-esr

Note

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

mozilla thunderbird UPGRADE

Affected: < 102.13

Fixed in: 102.13

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 102.13 (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.

debian debian linux MITIGATE

Affected: 10.0 · 11.0 · 12.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 10.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · kwin-zones · FIXED · 1.0.13-1.fc46 · FEDORA-2026-95888f332b · source

sudo dnf upgrade --advisory=FEDORA-2026-95888f332b

Fedora ELN · nginx-mod-brotli · FIXED · 1.0.0~rc-16.eln159 · FEDORA-2026-501a6a8273 · source

sudo dnf upgrade --advisory=FEDORA-2026-501a6a8273

Ubuntu 22.04 · firefox · NOT AFFECTED

Ubuntu 20.04 · firefox · FIXED · 115.0+build2-0ubuntu0.20.04.3

sudo apt update && sudo apt install --only-upgrade firefox dpkg --compare-versions "$(dpkg-query -W -f='${Version}' firefox)" ge "115.0+build2-0ubuntu0.20.04.3" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 20.04 · thunderbird · FIXED · 1:102.13.0+build1-0ubuntu0.20.04.1

sudo apt update && sudo apt install --only-upgrade thunderbird dpkg --compare-versions "$(dpkg-query -W -f='${Version}' thunderbird)" ge "1:102.13.0+build1-0ubuntu0.20.04.1" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 22.04 · thunderbird · FIXED · 1:102.13.0+build1-0ubuntu0.22.04.1

Debian 12 · firefox-esr · FIXED · 102.13.0esr-1~deb12u1

sudo apt update && sudo apt install --only-upgrade firefox-esr dpkg --compare-versions "$(dpkg-query -W -f='${Version}' firefox-esr)" ge "102.13.0esr-1~deb12u1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · firefox-esr · FIXED · 102.13.0esr-1

sudo apt update && sudo apt install --only-upgrade firefox-esr dpkg --compare-versions "$(dpkg-query -W -f='${Version}' firefox-esr)" ge "102.13.0esr-1" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · thunderbird · FIXED · 1:102.13.0-1~deb12u1

sudo apt update && sudo apt install --only-upgrade thunderbird dpkg --compare-versions "$(dpkg-query -W -f='${Version}' thunderbird)" ge "1:102.13.0-1~deb12u1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · thunderbird · FIXED · 1:102.13.0-1

sudo apt update && sudo apt install --only-upgrade thunderbird dpkg --compare-versions "$(dpkg-query -W -f='${Version}' thunderbird)" ge "1:102.13.0-1" && echo PATCHED || echo STILL-VULNERABLE

RHEL 7 · thunderbird · FIXED · thunderbird-102.13.0-2.el7_9

sudo dnf upgrade --advisory=RHSA-2023:4062 rpm -q thunderbird

RHEL 7 · firefox · FIXED · firefox-102.13.0-2.el7_9

sudo dnf upgrade --advisory=RHSA-2023:4079 rpm -q firefox

RHEL 8 · thunderbird · FIXED · thunderbird-102.13.0-2.el8_8

sudo dnf upgrade --advisory=RHSA-2023:4063 rpm -q thunderbird

RHEL 8 · firefox · FIXED · firefox-102.13.0-2.el8_8

sudo dnf upgrade --advisory=RHSA-2023:4076 rpm -q firefox

RHEL 8.1 Update Services for SAP Solutions · thunderbird · FIXED · thunderbird-102.13.0-2.el8_1

sudo dnf upgrade --advisory=RHSA-2023:4065 rpm -q thunderbird

Alpine 3.20 · firefox-esr · FIXED · firefox-esr-115.0-r0

apk add --upgrade firefox-esr apk info -v firefox-esr

Alpine 3.21 · firefox-esr · FIXED · firefox-esr-115.0-r0

apk add --upgrade firefox-esr apk info -v firefox-esr

Alpine 3.22 · firefox-esr · FIXED · firefox-esr-115.0-r0

apk add --upgrade firefox-esr apk info -v firefox-esr

Alpine 3.23 · firefox-esr · FIXED · firefox-esr-115.0-r0

apk add --upgrade firefox-esr apk info -v firefox-esr

Amazon Linux 2 · see advisory · FIXED · ALAS2-2023-2156 · source

sudo yum update --advisory=ALAS2-2023-2156

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Write-up: bugzilla.mozilla.org/show_bug.cgi?id=1816287

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-2023-37207?

firefox: upgrade to 115.0; firefox esr: upgrade to 102.13; thunderbird: upgrade to 102.13. Exact commands for each OS are on this page.

Is CVE-2023-37207 being exploited?

CVE-2023-37207 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-2023-37207 affect?

CVE-2023-37207 affects firefox, firefox esr, thunderbird. Severity is medium (CVSS 6.5). A website could have obscured the fullscreen notification by using a URL with a scheme handled by an external program, such as a mailto URL. This could have led to user confusion and possible spoofing attacks. This vulnerability affects Fir

How urgent is CVE-2023-37207?

Priority 44/100. CISA SSVC: public proof of concept; On your watchlist

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References

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