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

Reference page built from the source records below, each shown as its source publishes it. Dataset version ref-aa2b7b28f7b4, updated 2026-11-02T23:39:54.475Z.

CISA Known Exploited Vulnerabilities

Name
Apache Log4j2 Deserialization of Untrusted Data Vulnerability
Vendor
Apache
Product
Log4j2
Added to the catalog
2023-05-01
Due date for US federal agencies
2023-05-22
Weaknesses
CWE-917
Catalog version
2026.10.30

Apache Log4j2 contains a deserialization of untrusted data vulnerability due to the incomplete fix of CVE-2021-44228, where the Thread Context Lookup Pattern is vulnerable to remote code execution in certain non-default configurations.

Required action (CISA)

Apply updates per vendor instructions.

Ransomware use: CISA marks this vulnerability as known to be used in ransomware campaigns. CISA does not say which group used it.

Links in CISA's notes

Read on 2026-11-02T23:39:54.475Z under licence cisa-kev-cc0@b0067899 from https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

NVD analysis

Status
Analyzed
Published
2021-12-14T19:15:07.733
Last modified
2026-06-17T04:13:05.570
Weaknesses
CWE-917

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 resulting in an information leak and remote code execution in some environments and local code execution in all environments. Log4j 2.16.0 (Java 8) and 2.12.2 (Java 7) fix this issue by removing support for message lookup patterns and disabling JNDI functionality by default.

MetricScoreSeverityVectorScored by
CVSS 3.19CRITICALCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H[email protected] (Primary)
CVSS 3.19CRITICALCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H134c704f-9b21-4f2e-91b3-4a467353bcc0 (Secondary)
CVSS 2.05.1MEDIUMAV:N/AC:H/Au:N/C:P/I:P/A:P[email protected] (Primary)

References

This product uses the NVD API but is not endorsed or certified by the NVD.

Read on 2026-11-02T23:41:59.479Z under licence nvd-api-terms-of-use@ff2a5288 from https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2021-45046

CVE record

Title (CNA)
Apache Log4j2 Thread Context Message Pattern and Context Lookup Pattern vulnerable to a denial of service attack
Assigner
apache
State
PUBLISHED
Published
2021-12-14T16:55:09.000Z
Updated
2025-10-21T23:25:22.768Z
Problem types
CWE-917 Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection')

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 resulting in an information leak and remote code execution in some environments and local code execution in all environments. Log4j 2.16.0 (Java 8) and 2.12.2 (Java 7) fix this issue by removing support for message lookup patterns and disabling JNDI functionality by default.

References

Read on 2026-11-03T01:09:22.575Z under licence cve-terms-of-use@81bfa2f3 from https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2021/45xxx/CVE-2021-45046.json

Also known as / affected packages

GHSA-7rjr-3q55-vv33

Also known as: CVE-2021-45046. OSV.dev record, GitHub advisory.

  • Maven org.apache.logging.log4j:log4j-core: introduced 2.13.0, fixed 2.16.0
  • Maven org.apache.logging.log4j:log4j-core: introduced 2.4.0, fixed 2.12.2
  • Maven org.ops4j.pax.logging:pax-logging-log4j2: introduced 1.8.0, fixed 1.9.2
  • Maven org.ops4j.pax.logging:pax-logging-log4j2: introduced 1.10.0, fixed 1.10.8
  • Maven org.ops4j.pax.logging:pax-logging-log4j2: introduced 1.11.0, fixed 1.11.11
  • Maven org.ops4j.pax.logging:pax-logging-log4j2: introduced 2.0.0, fixed 2.0.12
  • Maven org.apache.logging.log4j:log4j-core: introduced 0, fixed 2.3.1

Read on 2026-11-03T00:57:10.395Z under licence ghsa-cc-by-4.0@9e5f1b3c from https://api.osv.dev/v1/vulns/GHSA-7rjr-3q55-vv33

Defensive techniques (MITRE D3FEND)

D3FEND maps these defensive techniques to the weakness (CWE) that NVD lists for this CVE, through the digital artifacts the weakness affects. D3FEND does not say they stop this vulnerability.

CWE-917: Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection')

D3FEND ontology version 1.6.0.

Read on 2026-11-03T00:03:21.049Z under licence d3fend-terms-of-use@f98cbc7e from https://d3fend.mitre.org/api/weakness/cwe/CWE-917.json

MITRE D3FEND™ knowledge graph. © 2025 The MITRE Corporation.
"The MITRE Corporation (MITRE) hereby grants you a non-exclusive, royalty-free license to use D3FEND for research, development, and commercial purposes. Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." Terms: https://d3fend.mitre.org/tou/

Sources and licences

  • CISA

    Source: CISA Catalog of Known Exploited Vulnerabilities, version 2026.10.30, CC0 1.0. Use of this data does not imply endorsement by CISA or DHS.

    CC0 1.0 Universal

  • National Vulnerability Database (NIST)

    This product uses the NVD API but is not endorsed or certified by the NVD.

    NVD API Terms of Use (NIST publications in the public domain, 17 U.S.C. 105)

  • CVE Program, The MITRE Corporation

    Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation. CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy.

    CVE Program Terms of Use ("CVE Usage" licence)

  • GitHub Advisory Database via OSV.dev

    GHSA-7rjr-3q55-vv33: GitHub Advisory Database, https://github.com/advisories/GHSA-7rjr-3q55-vv33. Licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/), provided as is, without warranties. Retrieved via OSV.dev (https://osv.dev/vulnerability/GHSA-7rjr-3q55-vv33), which enriches records; fields selected and reformatted by ransomware-tracker.com.

    CC BY 4.0

  • MITRE D3FEND

    MITRE D3FEND™ knowledge graph. © 2025 The MITRE Corporation.
    "The MITRE Corporation (MITRE) hereby grants you a non-exclusive, royalty-free license to use D3FEND for research, development, and commercial purposes. Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." Terms: https://d3fend.mitre.org/tou/

    MITRE D3FEND Terms of Use (site + knowledge graph); source repo MIT

Cite this page

Dragons Eye Ransomware Tracker, "CVE-2021-45046: Apache Log4j2 Deserialization of Untrusted Data Vulnerability",
entity page, dataset version ref-aa2b7b28f7b4, updated 2026-11-02T23:39:54.475Z,
https://ransomware-tracker.com/cve/CVE-2021-45046 (accessed 2026-11-03).
Underlying source: CISA Catalog of Known Exploited Vulnerabilities, version 2026.10.30.
Underlying source: National Vulnerability Database (NIST), CVE API 2.0, record last modified 2026-06-17T04:13:05.570.
Underlying source: CVE List (CVE Program, The MITRE Corporation), record updated 2025-10-21T23:25:22.768Z.
Underlying source: GitHub Advisory Database, GHSA-7rjr-3q55-vv33, via OSV.dev, modified 2026-10-02T20:30:05.438504645Z.
Underlying source: MITRE D3FEND, ontology version 1.6.0.

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