CVE-2021-45046: Apache Log4j2 Deserialization of Untrusted Data Vulnerability

Q: How do I fix CVE-2021-45046?

log4j: upgrade to 2.12.2, 2.16.0; computer vision annotation tool: mitigate or apply the listed mitigation; audio development kit: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2021-45046 being exploited?

Yes. CVE-2021-45046 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

Q: What does CVE-2021-45046 affect?

CVE-2021-45046 affects log4j, computer vision annotation tool, audio development kit. Severity is critical (CVSS 9.0). It was found that the fix to address CVE-2021-44228 in Apache Log4j 2.15.0 was incomplete in certain non-default configurations. This could allows attackers with control over Thread Context Map (MDC) input data when the logging configuratio

Q: How urgent is CVE-2021-45046?

Priority 100/100. Critical severity; EPSS top 1%: very likely to be exploited; Exploited in the wild (CISA KEV); Used in ransomware campaigns; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

100

Patch now

CRITICAL 9.0EXPLOITEDREMOTEWATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2021-45046 is a critical-severity flaw (CVSS 9.0) affecting log4j, computer vision annotation tool, audio development kit, reported as exploited in the wild. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

It was found that the fix to address CVE-2021-44228 in Apache Log4j 2.15.0 was incomplete in certain non-default configurations. This could allows attackers with control over Thread Context Map (MDC) input data when the logging configuration uses a non-default Pattern Layout with either a Context Lookup (for example, $${ctx:loginId}) or a Thread Context Map pattern (%X, %mdc, or %MDC) to craft malicious input data using a JNDI Lookup pattern resu

Why this priority

Critical severity
EPSS top 1%: very likely to be exploited
Exploited in the wild (CISA KEV)
Used in ransomware campaigns
Public exploit reference
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.0 (Critical)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	100.0% (top 1%)
CISA exploited list	Yes, fix due 2023-05-22, used in ransomware
Weakness	CWE-917
Published	2021-12-14
Last modified	2026-06-17

Publisher (CNA): Apache Software Foundation · Vendor: apache · cvat · intel

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

Am I affected?

Timeline

2021-12-14 19:15 UTCPublished CVE record published
2023-05-01Exploited Added to the CISA Known Exploited Vulnerabilities list
2023-05-22Deadline CISA due date for US federal agencies to patch
2026-06-17 04:13 UTCUpdated Record last modified

apache log4j UPGRADE

Affected: >= 2.0.1 and < 2.12.2 · >= 2.13.0 and < 2.16.0 · 2.0 · 2.0 beta9 · 2.0 rc1 · 2.0 rc2

Fixed in: 2.12.2, 2.16.0

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 2.12.2 (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.

cvat computer vision annotation tool 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 computer-vision-annotation-tool || rpm -q computer-vision-annotation-tool || computer-vision-annotation-tool --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

intel audio development kit 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 audio-development-kit || rpm -q audio-development-kit || audio-development-kit --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

intel datacenter 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 datacenter-manager || rpm -q datacenter-manager || datacenter-manager --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

intel genomics kernel library 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 genomics-kernel-library || rpm -q genomics-kernel-library || genomics-kernel-library --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

intel oneapi 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 oneapi || rpm -q oneapi || oneapi --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Maven · org.apache.logging.log4j:log4j-core · FIXED · 2.16.0 · vulnerable: >= 2.13.0, < 2.16.0 · source

Set org.apache.logging.log4j:log4j-core to 2.16.0 or later in pom.xml or build.gradle, then rebuild and redeploy.

Maven · org.ops4j.pax.logging:pax-logging-log4j2 · FIXED · 1.9.2 · vulnerable: >= 1.8.0, < 1.9.2 · source

Set org.ops4j.pax.logging:pax-logging-log4j2 to 1.9.2 or later in pom.xml or build.gradle, then rebuild and redeploy.

Fedora 46 · nemo · FIXED · 6.8.0-1.fc46 · FEDORA-2026-0edead723f · source

sudo dnf upgrade --advisory=FEDORA-2026-0edead723f

Fedora ELN · composer · FIXED · 2.11.1-1.eln159 · FEDORA-2026-cb4f992456 · source

sudo dnf upgrade --advisory=FEDORA-2026-cb4f992456

Ubuntu 22.04 · apache-log4j2 · NOT AFFECTED

Ubuntu 20.04 · apache-log4j2 · FIXED · 2.16.0-0.20.04.1

sudo apt update && sudo apt install --only-upgrade apache-log4j2 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' apache-log4j2)" ge "2.16.0-0.20.04.1" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · apache-log4j2 · FIXED · 2.16.0-1

sudo apt update && sudo apt install --only-upgrade apache-log4j2 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' apache-log4j2)" ge "2.16.0-1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · apache-log4j2 · FIXED · 2.16.0-1

sudo apt update && sudo apt install --only-upgrade apache-log4j2 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' apache-log4j2)" ge "2.16.0-1" && echo PATCHED || echo STILL-VULNERABLE

RHEL 6 · log4j · NOT AFFECTED

RHEL 7 · log4j · NOT AFFECTED

RHEL 8 · parfait:0.5/log4j12 · NOT AFFECTED

Amazon Linux 2 · see advisory · FIXED · ALAS2-2021-1731 · source

sudo yum update --advisory=ALAS2-2021-1731

Amazon Linux 1 · see advisory · FIXED · ALAS-2021-1553 · source

sudo yum update --advisory=ALAS-2021-1553

Public exploits and detection

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

GitHub PoC: lijiejie/log4j2_vul_local_scanner (85 stars)
GitHub PoC: cckuailong/Log4j_CVE-2021-45046 (22 stars)
GitHub PoC: mergebase/log4j-samples (14 stars)
Write-up: tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-log4j-qRuKNE
Write-up: www.oracle.com/security-alerts/cpuapr2022.html
Write-up: www.oracle.com/security-alerts/cpujan2022.html
Metasploit: Log4Shell HTTP Scanner
Nuclei scan template: Apache Log4j2 - Remote Code Injection

Verify at the official source NVD · CVE Program · CISA KEV catalog · 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-2021-45046?

log4j: upgrade to 2.12.2, 2.16.0; computer vision annotation tool: mitigate or apply the listed mitigation; audio development kit: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-45046 being exploited?

Yes. CVE-2021-45046 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

What does CVE-2021-45046 affect?

CVE-2021-45046 affects log4j, computer vision annotation tool, audio development kit. Severity is critical (CVSS 9.0). It was found that the fix to address CVE-2021-44228 in Apache Log4j 2.15.0 was incomplete in certain non-default configurations. This could allows attackers with control over Thread Context Map (MDC) input data when the logging configuratio

How urgent is CVE-2021-45046?

Priority 100/100. Critical severity; EPSS top 1%: very likely to be exploited; Exploited in the wild (CISA KEV); Used in ransomware campaigns; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Apache Log4j vulnerabilities · Intel vulnerabilities

Related CVEs

CVE-2026-34478 HIGH 7.5 UPGRADE Apache Log4j Core's Rfc5424Layout https://logging.apache.org/log4j/2.x/manual/layouts.html#RFC5424Layout , in
CVE-2026-34480 HIGH 7.5 UPGRADE Apache Log4j Core's XmlLayout https://logging.apache.org/log4j/2.x/manual/layouts.html#XmlLayout , in version
CVE-2026-34481 HIGH 7.5 UPGRADE Apache Log4j's JsonTemplateLayout https://logging.apache.org/log4j/2.x/manual/json-template-layout.html , in
CVE-2026-34477 MEDIUM 5.9 UPGRADE The fix for CVE-2025-68161 https://logging.apache.org/security.html#CVE-2025-68161 was incomplete: it addres
CVE-2026-34479 HIGH 7.5 UPGRADE The Log4j1XmlLayout from the Apache Log4j 1-to-Log4j 2 bridge fails to escape characters forbidden by the XML

References

← Back to latest CVEs