CVE-2021-4104
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Deserialization of untrusted data in JMSAppender in Apache Log4j 1.2
rank 60 = 27 + 19 + 0 + 14 + 0
rank@v1 · this cycle
Someone is already using it
CISA KEV catalog · public proof-of-concept · FIRST EPSS
EPSS 0.80599 · without this subject the record ranks 33
What it costs you if it fires
NVD CVSS base score, then the CNA's own
CVSS 7.5, from NVD · without this subject the record ranks 41
It is getting worse, not staying still
FIRST EPSS series, rescorings and bad loads removed
no persisting rise in 365 days · without this subject the record ranks 60
How much of the world it touches
NVD CPE configurations
64 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 60
Hindsight · the state
Foresight · where to check next
log4j 1.x is one instance of CWE-502, deserialization of untrusted data. The index holds 3513 prior instances of this class, 76 KEV-listed. 5 neighbors share the mechanism; each carries its own record state. taxonomy@v1
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CISA KEV & Federal Remediation Deadline from the record and CISA
The fix, and how long it's been waiting.
Show full BOD 26-04 deadline
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Exploit Status & Known PoCs a ladder, not a score
Current rung: Proof-of-concept published · 2 public repositories, 2021-12-14.
- RUNG 1Nothing observed in held sources
- RUNG 2Proof-of-concept published · 2 public repositories2021-12-14receipt
- RUNG 3Exploited in the wild · CISA KEV listed
- RUNG 4Ransomware campaign use known
Affected & Fixed Versions as published
Show all 64 published ranges
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$4.02M = $4.99M incident cost x 1 exposure x 0.80599 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.
What it is stated by the CNA
JMSAppender in Log4j 1.2 is vulnerable to deserialization of untrusted data when the attacker has write access to the Log4j configuration. The attacker can provide TopicBindingName and TopicConnectionFactoryBindingName configurations causing JMSAppender to perform JNDI requests that result in remote code execution in a similar fashion to CVE-2021-44228. Note this issue only affects Log4j 1.2 when specifically configured to use JMSAppender, which is not the default. Apache Log4j 1.2 reached end of life in August 2015. Users should upgrade to Log4j 2 as it addresses numerous other issues from the previous versions. receipt
NVD's analysis a second authority
- severity
- 7.5 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
- weakness
- CWE-502
- affected versions
- apache log4j 1.2; fedoraproject fedora 35; redhat codeready studio 12.0; and 61 more, listed in full below
- also scored by
- 7.5 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
check it yourself cve.org github.com access.redhat.com kb.cert.org openwall.com oracle.com +8 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 62 observations
62 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
log4j 1.x is one instance of CWE-502, deserialization of untrusted data. The index holds 3513 prior instances of this class, 76 KEV-listed. 5 neighbors share the mechanism; each carries its own record state. cwe-consequences@4.20
3513 records in this class held. The six above are ranked by exploit maturity, then recency.
Siblings and hubs
Records related to this one
Its defect family
apache software foundation apache log4j
Of the 5 records in this family, this is the only one whose title names jmsappender 1.2.
Grouped by shared product and weakness, not by shared vulnerability. Each record's own state is on its own page.
Family membership: computed, pro@dim2000
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What usually comes next
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