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Log4jFramework / library · Apache

CVE-2021-45105

MEDIUM · 5.9 CVSS v3.1 Published 2021-12-18
Fix available
A fix is available. Upgrade to 2.3.1 / 2.7.0 or later.
See remediation →
68/100
Remediation priority · Elevated
High EPSS Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-20

The application accepts input without confirming it is well-formed or within expected bounds, so malformed data can push the program into states its author never anticipated. Attackers probe these gaps to trigger crashes, bypass logic, or feed tainted values into more dangerous operations downstream. Remediating it well means validating and normalising every input at the boundary against a strict allow-list — not merely filtering known-bad values.

General guidance for the improper input validation class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Log4jFramework / library
Affected:>= 2.0, < 2.3.1>= 2.4, < 2.12.3>= 2.13.0, <= 2.16.0
Debian LinuxOperating system
Affected:= 10.0= 11.0
Cloud ManagerApplication
Affected:all versions
Email SecurityApplication
Affected:<= 10.0.12
Network Security ManagerApplication
Affected:>= 2.0, < 3.0
Web Application FirewallApplication
Affected:>= 3.0.0, < 3.1.0
6bk1602 0aa12 0tp0 FirmwareOperating system
Affected:< 2.7.0
6bk1602 0aa22 0tp0 FirmwareOperating system
Affected:< 2.7.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2.3.1 / 2.7.0 / 2.12.3 or later
Fixed in 2.3.12.7.02.12.3
Vendor patch www.oracle.com →
Recommended fix High confidence

Log4j 2.17.0 (or 2.12.3/2.3.1 depending on your baseline branch)

  1. 1. Identify all instances of Log4j in your environment by scanning for log4j-core*.jar or log4j-api*.jar files
  2. 2. For each affected Log4j installation, determine the current version (check META-INF/MANIFEST.MF within the JAR file for Implementation-Version)
  3. 3. If running Log4j 2.0 through 2.3.0: upgrade to Log4j 2.3.1
  4. 4. If running Log4j 2.4 through 2.12.2: upgrade to Log4j 2.12.3
  5. 5. If running Log4j 2.13.0 through 2.16.0: upgrade to Log4j 2.17.0 (or latest 2.x stable release)
  6. 6. Replace the old log4j-core and log4j-api JAR files with the new versions in all application lib directories, WAR files, and nested dependencies
  7. 7. Restart all applications and services using the updated Log4j libraries
  8. 8. Verify the upgrade was successful by checking that the application now loads Log4j version 2.17.0, 2.12.3, or 2.3.1
Caveat Log4j 2.17.0 removes the lookup feature entirely by default; if your application relies on ${...} syntax for configuration, test thoroughly before production deployment

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,600. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-45105 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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