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CVE-2017-5434: A use-after-free vulnerability occurs when redirecting focus handling which results in a potentially exploitab

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CRITICAL 9.8REMOTEWATCHLISTMITIGATEMITIGATEMITIGATE

CVE-2017-5434 is a critical-severity flaw (CVSS 9.8) affecting enterprise linux desktop, enterprise linux server, enterprise linux workstation. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A use-after-free vulnerability occurs when redirecting focus handling which results in a potentially exploitable crash. This vulnerability affects Thunderbird < 52.1, Firefox ESR < 45.9, Firefox ESR < 52.1, and Firefox < 53.

Why this priority

  • Critical severity
  • Public exploit reference
  • Remotely exploitable, no login, no user action
  • On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score9.8 (Critical)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionNone
EPSS exploit chance3.5% (top 11%)
CISA exploited listNo
WeaknessCWE-416
Published2018-06-11
Last modified2026-06-17
Publisher (CNA): Mozilla Corporation · Vendor: debian · mozilla · redhat

Share: LinkedIn · X · Reddit

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

redhat enterprise linux desktop MITIGATE
Affected: 6.0 · 7.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 6.0
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.
redhat enterprise linux server MITIGATE
Affected: 6.0 · 7.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 6.0
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.
redhat enterprise linux workstation MITIGATE
Affected: 6.0 · 7.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 6.0
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.
debian debian linux MITIGATE
Affected: 8.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 8.0
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.
mozilla firefox UPGRADE
Affected: < 45.9.0 · < 53.0 · 52.0
Fixed in: 45.9.0, 53.0
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy firefox || rpm -q firefox || firefox --version
2. UPGRADE to 45.9.0 (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 thunderbird UPGRADE
Affected: < 52.1.0
Fixed in: 52.1.0
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy thunderbird || rpm -q thunderbird || thunderbird --version
2. UPGRADE to 52.1.0 (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.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.
Fedora 46 · librepo · FIXED · 1.21.3-1.fc46 · FEDORA-2026-c502136ca7 · source
sudo dnf upgrade --advisory=FEDORA-2026-c502136ca7
Debian 12 · firefox-esr · FIXED · 45.9.0esr-1
sudo apt update && sudo apt install --only-upgrade firefox-esr dpkg --compare-versions "$(dpkg-query -W -f='${Version}' firefox-esr)" ge "45.9.0esr-1" && echo PATCHED || echo STILL-VULNERABLE
Debian 13 · firefox-esr · FIXED · 45.9.0esr-1
sudo apt update && sudo apt install --only-upgrade firefox-esr dpkg --compare-versions "$(dpkg-query -W -f='${Version}' firefox-esr)" ge "45.9.0esr-1" && echo PATCHED || echo STILL-VULNERABLE
RHEL 6 · firefox · FIXED · firefox-52.1.0-2.el6_9
sudo dnf upgrade --advisory=RHSA-2017:1104 rpm -q firefox
RHEL 6 · thunderbird · FIXED · thunderbird-52.1.0-1.el6_9
sudo dnf upgrade --advisory=RHSA-2017:1201 rpm -q thunderbird
RHEL 7 · firefox · FIXED · firefox-52.1.0-2.el7_3
sudo dnf upgrade --advisory=RHSA-2017:1106 rpm -q firefox
RHEL 7 · thunderbird · FIXED · thunderbird-52.1.0-1.el7_3
sudo dnf upgrade --advisory=RHSA-2017:1201 rpm -q thunderbird
RHEL 5 · firefox · DEFERRED

Public exploits and detection

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

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-2017-5434?

enterprise linux desktop: mitigate or apply the listed mitigation; enterprise linux server: mitigate or apply the listed mitigation; enterprise linux workstation: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2017-5434 being exploited?

CVE-2017-5434 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-2017-5434 affect?

CVE-2017-5434 affects enterprise linux desktop, enterprise linux server, enterprise linux workstation. Severity is critical (CVSS 9.8). A use-after-free vulnerability occurs when redirecting focus handling which results in a potentially exploitable crash. This vulnerability affects Thunderbird < 52.1, Firefox ESR < 45.9, Firefox ESR < 52.1, and Firefox < 53.

How urgent is CVE-2017-5434?

Priority 72/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Debian vulnerabilities · Mozilla Firefox vulnerabilities · Mozilla Thunderbird vulnerabilities

Related CVEs

References

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