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

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

• Documented mitigation — www.openwall.com (NIST National Vulnerability Database)
• Documented mitigation — logging.apache.org (NIST National Vulnerability Database)
• Documented patch — www.oracle.com (NIST National Vulnerability Database)
• Maven Org.apache.logging.log4j:log4j-core: fixed in version 2.16.0 — github.com (GitHub Security Advisories)
• Maven Org.apache.logging.log4j:log4j-core: fixed in version 2.12.2 — github.com (GitHub Security Advisories)
• Maven Org.apache.logging.log4j:log4j-core: fixed in version 2.3.1 — github.com (GitHub Security Advisories)
• Maven Org.ops4j.pax.logging:pax-logging-log4j2: fixed in version 1.9.2 — github.com (GitHub Security Advisories)
• Maven Org.ops4j.pax.logging:pax-logging-log4j2: fixed in version 1.10.8 — github.com (GitHub Security Advisories)
• Maven Org.ops4j.pax.logging:pax-logging-log4j2: fixed in version 1.11.11 — github.com (GitHub Security Advisories)
• Maven Org.ops4j.pax.logging:pax-logging-log4j2: fixed in version 2.0.12 — github.com (GitHub Security Advisories)

CISA required action CISA

Apply updates per vendor instructions.

US federal deadline: May 22, 2023 — passed 1242 day(s) ago

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

1. Identify exposed assets running the affected vendor/product/version combinations (Apache Software Foundation Log4j, Cvat Computer Vision Annotation Tool, Debian Debian Linux…).
2. Treat as emergency remediation: the CVE is in CISA KEV (confirmed exploitation).
3. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
4. Apply the fixed version or the patch documented under Remediation.
5. EPSS ahead of 100% of scored CVEs: prioritize it in the patch queue.
6. Search available logs for exploit probes matching the vulnerability class (injection), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-917 · Expression Language Injection

Other CVEs with this weakness →

CISA KEV details CISA

CISA lists a CVE once it has evidence of exploitation against real targets.

CISA records ransomware use only for campaigns it has confirmed, so “Unknown” means unrecorded, not ruled out. The deadline binds US federal agencies; for everyone else it is a reference date.

Public exploits, PoCs and detection templates

Public code that demonstrates or tests the flaw raises the odds of mass exploitation — and Nuclei templates help find vulnerable assets in your environment.

Warning: public PoCs are sometimes disguised malware. Use them only for authorized testing in an isolated environment. This portal does not host exploit code — it only points to the sources.

EPSS over time FIRST

Oct 12, 2026 → Oct 14, 2026 · 3 reading(s) · max 99.98%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

• Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
• Look for parameters with command/query metacharacters and unexpected child processes of the service.
• Hunt retroactively in logs from before May 1, 2023 (KEV listing): exploitation may have started earlier.

Timeline

What happened to this CVE, newest first.

• 2026
• Fix documented
  Oct 13, 2026 · GitHub Security Advisories
• Affected products added · maven/org.apache.logging.log4j:log4j-core, maven/org.ops4j.pax.logging:pax-logging-log4j2
  Oct 13, 2026 · GitHub Security Advisories
• Affected products added · apache software foundation/apache log4j
  Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
• SSVC assessment updated
  Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
• Record published
  Oct 13, 2026
• Fix documented
  Oct 13, 2026 · NIST National Vulnerability Database
• Affected products added · apache/log4j, cvat/computer vision annotation tool, intel/audio development kit, intel/datacenter manager, intel/genomic
  Oct 13, 2026 · NIST National Vulnerability Database
• CVSS changed · 9.0
  Oct 13, 2026 · NIST National Vulnerability Database
• Source status changed · → Analyzed
  Oct 13, 2026 · NIST National Vulnerability Database
• Added to CISA KEV (detected)
  Oct 13, 2026 · CISA Known Exploited Vulnerabilities
• Record created in this database
  Oct 13, 2026 · CISA Known Exploited Vulnerabilities
• 2023
• Added to CISA KEV catalog
  Apr 30, 2023 · CISA
• 2021
• CVE published
  Dec 14, 2021 · apache

Source activity

Repeated readings are counted rather than listed.

• 2× References added · Oct 13, 2026 – Oct 13, 2026
• 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

32 on the record

• logging.apache.org/log4j/2.x/security.html
  Mitigation, Release Notes, Vendor Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• www.oracle.com/security-alerts/cpujan2022.html
  Patch, Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
• www.openwall.com/lists/oss-security/2021/12/14/4
  Mailing List, Mitigation, Third Party Advisory, mailing-list, x_refsource_MLIST, NIST National Vulnerability Database
• www.cisa.gov/known-exploited-vulnerabilities-catalog
  US Government Resource, NIST National Vulnerability Database
• www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00646.html
  Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• cert-portal.siemens.com/productcert/pdf/ssa-397453.pdf
  Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• www.oracle.com/security-alerts/cpuapr2022.html
  Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
• psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0032
  Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• security.gentoo.org/glsa/202310-16
  Third Party Advisory, NIST National Vulnerability Database
• lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EOKP
  Mailing List, Release Notes, vendor-advisory, x_refsource_FEDORA, NIST National Vulnerability Database
• www.openwall.com/lists/oss-security/2021/12/14/4
  GitHub Security Advisories
• lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/EOKPQG
  GitHub Security Advisories
• lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/SIG7FZ
  GitHub Security Advisories
• github.com/advisories/GHSA-7rjr-3q55-vv33
  GitHub Security Advisories
• www.oracle.com/security-alerts/alert-cve-2021-44228.html
  Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• nvd.nist.gov/vuln/detail/CVE-2021-45046
  GitHub Security Advisories
• tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-log4j-q
  Third Party Advisory, vendor-advisory, x_refsource_CISCO, NIST National Vulnerability Database
• www.cve.org/CVERecord
  Not Applicable, x_refsource_MISC, NIST National Vulnerability Database
• sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-log4j-q
  GitHub Security Advisories
• cert-portal.siemens.com/productcert/pdf/ssa-661247.pdf
  Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• github.com/apache/logging-log4j2/compare/rel/2.3...rel/2.3.1
  GitHub Security Advisories
• www.openwall.com/lists/oss-security/2021/12/15/3
  GitHub Security Advisories
• www.kb.cert.org/vuls/id/930724
  Third Party Advisory, US Government Resource, third-party-advisory, x_refsource_CERT-VN, NIST National Vulnerability Database
• www.debian.org/security/2021/dsa-5022
  Third Party Advisory, vendor-advisory, x_refsource_DEBIAN, NIST National Vulnerability Database
• cert-portal.siemens.com/productcert/pdf/ssa-479842.pdf
  Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• www.openwall.com/lists/oss-security/2021/12/15/3
  Mailing List, Third Party Advisory, mailing-list, x_refsource_MLIST, NIST National Vulnerability Database
• www.openwall.com/lists/oss-security/2021/12/18/1
  Mailing List, Third Party Advisory, mailing-list, x_refsource_MLIST, NIST National Vulnerability Database
• lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SIG7
  Mailing List, Release Notes, vendor-advisory, x_refsource_FEDORA, NIST National Vulnerability Database
• cert-portal.siemens.com/productcert/pdf/ssa-714170.pdf
  Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• www.oracle.com/security-alerts/cpujul2022.html
  Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
• www.openwall.com/lists/oss-security/2021/12/18/1
  GitHub Security Advisories
• logging.apache.org/security.html
  GitHub Security Advisories

Elsewhere on this site

Related CVEs (same products)

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• Medium CVE-2026-49844 Apache Log4j API: Improper serialization of non-finite floating-point values in MapMessage.asJson() Jul 10, 2026
• Medium CVE-2026-14355 ext/openssl: Memory corruption in openssl_encrypt with AES-WRAP-PAD Jul 3, 2026
• Medium CVE-2026-58373 CVAT < 2.69.0 - Missing Authorization on Quality Reports parent_id Filter Leaks Cross-Organization Report Existence Jun 30, 2026
• Medium CVE-2026-56968 Use of Uninitialized Resource in Gnu Sasl Jun 23, 2026
• Medium CVE-2026-54231 Abrt: unsanitized systemd journal content written to dump directory files enables content injection Jun 13, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

• No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
• No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
• No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2021-45046 is "Apache Log4j2 Deserialization of Untrusted Data Vulnerability", rated Critical. It affects Log4j (Apache Software Foundation); versions are in the scope table. It is in CISA KEV: there is evidence of real-world exploitation. CVSS 9.0 describes technical severity. EPSS 99.98% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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