PatchTheCVECVE-2021-45105: Apache Log4j2 versions 2.0-alpha1 through 2.16.0 (excluding 2.12.3 and 2.3.1) did not protect from uncontrolle
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This week
MEDIUM 5.9REMOTEWATCHLISTUPGRADEMITIGATEMITIGATE
CVE-2021-45105 is a medium-severity flaw (CVSS 5.9) affecting log4j, cloud manager, debian linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
Apache Log4j2 versions 2.0-alpha1 through 2.16.0 (excluding 2.12.3 and 2.3.1) did not protect from uncontrolled recursion from self-referential lookups. This allows an attacker with control over Thread Context Map data to cause a denial of service when a crafted string is interpreted. This issue was fixed in Log4j 2.17.0, 2.12.3, and 2.3.1.
Why this priority
- EPSS top 1%: very likely to be exploited
- Remotely exploitable, no login, no user action
- On your watchlist
A fixed release or distro patch exists.
Last updated 2026-08-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
apache log4j UPGRADE
Affected: >= 2.0 and < 2.3.1 · >= 2.4 and < 2.12.3 · >= 2.13.0 and <= 2.16.0
Fixed in: 2.3.1, 2.12.3
Safe to downgrade to: a release before 2.0
1. Check installed version
apt-cache policy log4j || rpm -q log4j || log4j --version
2. UPGRADE to 2.3.1 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade log4j
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade log4j
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 2.0 (Debian / Ubuntu)
apt-cache madison log4j
sudo apt install log4j=<VERSION_BEFORE_2.0>
sudo apt-mark hold log4j
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list log4j
sudo dnf downgrade log4j-<VERSION_BEFORE_2.0>
sudo dnf versionlock add log4j
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.
netapp cloud manager MITIGATE
Affected: all versions
Fixed in: no fixed release known
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy cloud-manager || rpm -q cloud-manager || cloud-manager --version
No fixed or unaffected release known
Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.
debian debian linux MITIGATE
Affected: 10.0 · 11.0
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.
sonicwall email security UPGRADE
Affected: <= 10.0.12
Fixed in: newer than 10.0.12
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy email-security || rpm -q email-security || email-security --version
2. UPGRADE to newer than 10.0.12 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade email-security
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade email-security
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
sonicwall network security manager UPGRADE
Affected: >= 2.0 and < 3.0
Fixed in: 3.0
Safe to downgrade to: a release before 2.0
1. Check installed version
apt-cache policy network-security-manager || rpm -q network-security-manager || network-security-manager --version
2. UPGRADE to 3.0 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade network-security-manager
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade network-security-manager
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 2.0 (Debian / Ubuntu)
apt-cache madison network-security-manager
sudo apt install network-security-manager=<VERSION_BEFORE_2.0>
sudo apt-mark hold network-security-manager
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list network-security-manager
sudo dnf downgrade network-security-manager-<VERSION_BEFORE_2.0>
sudo dnf versionlock add network-security-manager
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.
sonicwall web application firewall UPGRADE
Affected: >= 3.0.0 and < 3.1.0
Fixed in: 3.1.0
Safe to downgrade to: a release before 3.0.0
1. Check installed version
apt-cache policy web-application-firewall || rpm -q web-application-firewall || web-application-firewall --version
2. UPGRADE to 3.1.0 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade web-application-firewall
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade web-application-firewall
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 3.0.0 (Debian / Ubuntu)
apt-cache madison web-application-firewall
sudo apt install web-application-firewall=<VERSION_BEFORE_3.0.0>
sudo apt-mark hold web-application-firewall
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list web-application-firewall
sudo dnf downgrade web-application-firewall-<VERSION_BEFORE_3.0.0>
sudo dnf versionlock add web-application-firewall
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.
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.
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-2021-45105?
log4j: upgrade to 2.3.1, 2.12.3; cloud manager: mitigate or apply the listed mitigation; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.
Is CVE-2021-45105 being exploited?
CVE-2021-45105 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-2021-45105 affect?
CVE-2021-45105 affects log4j, cloud manager, debian linux. Severity is medium (CVSS 5.9). Apache Log4j2 versions 2.0-alpha1 through 2.16.0 (excluding 2.12.3 and 2.3.1) did not protect from uncontrolled recursion from self-referential lookups. This allows an attacker with control over Thread Context Map data to cause a denial of
How urgent is CVE-2021-45105?
Priority 56/100. EPSS top 1%: very likely to be exploited; Remotely exploitable, no login, no user action; On your watchlist
Software pages
Apache Log4j vulnerabilities · Debian vulnerabilities · SonicWall vulnerabilities
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