CVE-2021-45105
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Apache Log4j2 does not always protect from infinite recursion in lookup evaluation
rank 56 = 30 + 15 + 1 + 10 + 0
rank@v1 · this cycle
Someone is already using it
CISA KEV catalog · public proof-of-concept · FIRST EPSS
EPSS 0.99999 · without this subject the record ranks 26
What it costs you if it fires
NVD CVSS base score, then the CNA's own
CVSS 5.9, from NVD · without this subject the record ranks 41
It is getting worse, not staying still
FIRST EPSS series, rescorings and bad loads removed
rose on 2025-07-22 · without this subject the record ranks 55
How much of the world it touches
NVD CPE configurations
20 products in the CPE ranges · without this subject the record ranks 46
Someone else already set the date
CISA KEV remediation due date
no CISA due date · without this subject the record ranks 56
$3.05M = $4.99M incident cost x 0.6121449559255632 exposure x 0.99999 likelihood
udv@v1 · unaudited · wrong for you until you say what you run
$4.99M is the cost of a breach that happened, from IBM Cost of a Data Breach Report 2026, global average. It is not the value of any asset of yours. That average already covers breaches of every severity, so scaling it by exposure understates a partial-impact record. That is an assumption, not a measurement. Your own asset value goes in the decision record.
Hindsight · the state
Foresight · where to check next
log4j2 is one instance of CWE-20, improper input validation. The index holds 13347 prior instances of this class, 73 KEV-listed. 6 neighbors share the mechanism; each carries its own record state. taxonomy@v1
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Harm, if it fires from the vector and the weakness
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CISA KEV & Federal Remediation Deadline from the record and CISA
The fix, and how long it's been waiting.
Exploit Status & Known PoCs a ladder, not a score
Current rung: Proof-of-concept published · 9 public repositories, 2021-12-18.
- RUNG 1Nothing observed in held sources
- RUNG 2Proof-of-concept published · 9 public repositories2021-12-18receipt
- RUNG 3Exploited in the wild · CISA KEV listed
- RUNG 4Ransomware campaign use known
Affected & Fixed Versions as published
Show all 20 published ranges
A rung lights from a row in the index, never from an assessment. "Held sources" is the true scope of the claim: this index reads the CVE record, NVD, CISA KEV, FIRST's EPSS and public proof-of-concept repositories, and it does not observe attacks.
What it is stated by the CNA
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. receipt
NVD's analysis a second authority
- severity
- 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- weakness
- CWE-20; CWE-674
- affected versions
- apache log4j >= 2.0 < 2.3.1; apache log4j >= 2.4 < 2.12.3; apache log4j >= 2.13.0 <= 2.16.0; and 17 more, listed in full below
- also scored by
- 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
check it yourself logging.apache.org psirt.global.sonicwall.com kb.cert.org tools.cisco.com openwall.com debian.org +7 morereceipt
Dated events
Movement the material steps
This score more than doubled inside 72 hours. Both observations are in the full history below.
Show all 99 observations
99 observations held. A highlighted step crossed a promotion threshold. A step marked with a scoring model moved because the instrument was replaced, not because the vulnerability changed. receipt
The pattern, elsewhere
log4j2 is one instance of CWE-20, improper input validation. The index holds 13347 prior instances of this class, 73 KEV-listed. 6 neighbors share the mechanism; each carries its own record state. [email protected]
13347 records in this class held. The six above are ranked by exploit maturity, then recency.
Siblings and hubs
Records related to this one
No record cites this identifier and it carries no alias. Its defect family is below.
Its defect family
apache software foundation apache log4j2
Of the 3 records in this family, this is the only one with public proof-of-concept code, and it holds 9 references to it.
Grouped by shared product and weakness, not by shared vulnerability. Each record's own state is on its own page.
Family membership: held values
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Browse the index from here
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What usually comes next
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