CVE-2021-45046 · Log4Shell bypass
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Apache Log4j2 Thread Context Message Pattern and Context Lookup Pattern vulnerable to a denial of service attack
rank 83 = 40 + 23 + 0 + 14 + 6
rank@v1 · act now
Someone is already using it
CISA KEV catalog · public proof-of-concept · FIRST EPSS
EPSS 0.99977 · CISA KEV listed · without this subject the record ranks 43
What it costs you if it fires
NVD CVSS base score, then the CNA's own
CVSS 9.0, from NVD · without this subject the record ranks 60
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 83
How much of the world it touches
NVD CPE configurations
63 products in the CPE ranges · without this subject the record ranks 69
Someone else already set the date
CISA KEV remediation due date
CISA remediation date held · without this subject the record ranks 77
Hindsight · the state
Foresight · where to check next
This record is one instance of CWE-917, improper neutralization of special elements used in an expression language statement ('expression language injection'). The index holds 209 prior instances of this class, 8 KEV-listed. The nearest of its KEV-listed records are drawn beside this. 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: Ransomware campaign use known, 2023-05-01.
Affected & Fixed Versions as published
Show all 63 published ranges
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$4.99M = $4.99M incident cost x 1 exposure x 0.99977 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
Log4Shell bypass is the common name for CVE-2021-45046. 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. cve-aliases@2026-08-27
Read the rest of the CNA's description
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.
NVD's analysis a second authority
- severity
- 9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
- weakness
- CWE-917
- affected versions
- apache log4j >= 2.0.1 < 2.12.2; apache log4j >= 2.13.0 < 2.16.0; apache log4j 2.0; and 60 more, listed in full below
- also scored by
- 9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
check it yourself psirt.global.sonicwall.com oracle.com cve.org openwall.com logging.apache.org kb.cert.org +14 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 59 observations
59 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 full biography
Listed by CISA 503 days after it published, exploit probability more than doubled between 2021-12-15 and 2021-12-16 (0.05553 → 0.24229) and the record had been public for 4 years, 8 months when this index was last written.
No material movement in 81 days as of the last ingest this index recorded.
The pattern, elsewhere
This record is one instance of CWE-917, improper neutralization of special elements used in an expression language statement ('expression language injection'). The index holds 209 prior instances of this class, 8 KEV-listed. The nearest of its KEV-listed records are drawn beside this. cwe-consequences@4.20
"Matches n of m" counts the attributes the two records can both be compared on: the CVSS metrics they share a version of, any weakness class beyond this one, and the vendor. fit-rules@v1
209 records in this class held. The six above are drawn from the ones CISA has listed as exploited, ranked by how much of the record matches this one. That is why every one of them is KEV-listed: the pool is, so the colour on those spokes says nothing the pool has not already said.
No curated product neighbourhood is held for this product, so the records above are the nearest this index can name. The neighbourhood table covers a small set of products and is extended by hand.
Siblings and hubs
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What usually comes next
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