Vulnerability · CVE-2021-45105
Apache log4j Improper Input Validation
Published Dec 22, 2021 · catalog updated Dec 22, 2021 · Apache Log4j2
Patch now
CVE-2021-45105 is in the CISA known-exploited catalog. Confirm Apache Log4j2 against the vendor advisory and apply that fix. The CVSS score does not change the priority.
Gaps on this record
- No version range is stored. A customer cannot check an installed version against this record.
- Severity
- Unknown—
- Known exploitation
- CISA KEV and VulnCheck KEV
- EPSS
- 100.00%
- Remediation
- Remediation guidance
- Affected products
- vendor Apache Log4j2
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. Initial-access exploit intelligence.
Are you affected?
Enter the version you run. The result uses only the ranges stored on this record.
The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.
- vendor Apache Log4j2version unspecified
How to fix CVE-2021-45105
Recommended remediation
Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.
Official advisories
What to do
Three questions, each answered from this record only. Confirm the vendor advisory before you patch.
Should you patch?
CVE-2021-45105 is in the CISA known-exploited catalog. Confirm Apache Log4j2 against the vendor advisory and apply that fix. The CVSS score does not change the priority.
Which versions are affected?
Affected version ranges are not on this record. Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.
What should an analyst verify?
No weakness class is stored. EPSS 100.00%. The CISA KEV listing is the exploitation evidence. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.
Code
The project this record applies to. Exploit listings stay in References.
No public source repository is identified for this product.
Timeline
Detection, updates, and resolution for this record.
Dec 22, 2021 · CISA KEV
Known exploited
Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.
Oct 15, 2026 · Apache Software Foundation
Detected
Named on the public Apache Software Foundation page.
Sources
- Apache Software FoundationVendor advisoryCVE-2021-45105
CVE-2021-45105 is named on the public Apache Software Foundation page.
logging.apache.org - CVE.orgVulnerability recordCVE-2021-45105
Official CVE identifier
cve.org - FIRST EPSSExploitation probabilityCVE-2021-45105
30-day exploitation probability 100.0%
first.org - VulnCheck KEVConfirmed exploitationCVE-2021-45105
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 interpr
vulncheck.com
References
Freshness
Last verified in this catalog Oct 17, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.