Threats / Apache / CVE-2021-45046
CVE-2021-45046
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-09-19
Apache Log4j2 vulnerability
Apache Log4j2 contains a deserialization vulnerability in the Thread Context Lookup Pattern due to incomplete remediation of CVE-2021-44228, enabling remote code execution in non-default configurations.
Verdict
Today item, not a backlog item.
This vulnerability allows unauthenticated remote code execution through crafted input to the Thread Context Lookup Pattern. The incomplete fix of the original Log4j2 flaw leaves a secondary attack vector accessible in certain deployments, with active exploitation and ransomware campaigns documented.
CISA KEV Yes · 2023-05-015Ransomware use Flagged5EPSS 0.99977 (verify live)6Exploit Weaponized · public PoC7CVSS 9 (CISA)4CISA SSVC Exploitation: active · Automatable: no · Impact: total4
01
Is it exploitable?
— the evidence, ranked above the scoreExploit available
Fully weaponized — public exploit code is cataloged for this vulnerability.We link the existence of the exploit; we do not host or redistribute payloads.
Reported exploitation
27 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2023-05-01), flagged for known ransomware use.
Probability (EPSS)
EPSS 0.99977 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 9 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H) · Affected: Apache, Log4j2. Confirm exact fixed builds in the vendor advisory.CVSS — CISA-assigned via the ADP container (CVE.org), version 3.1; the CNA left no metrics, so CISA's own score is used ahead of NVD.
Weakness (CWE)
Mapped to CWE-917 Expression Language Injection — weakness family: Injection.CWE — CNA-assigned (CVE.org); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: totalCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 503 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
Public exploit available
Public exploit tooling is catalogued for this CVE (a public proof-of-concept / detection template). Catalog entries: Metasploit module, nuclei template. We link the catalog page(s) only — no payload or code is hosted or restated here.Link, never host — the catalog page is the source; basicsecurity.net does not redistribute payloads.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious input string containing a Thread Context Lookup Pattern expression that triggers deserialization of untrusted data.
Business
An attacker gains arbitrary code execution on servers running vulnerable Log4j2 versions, enabling data theft, system compromise, or lateral movement.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I deliver the payload through application logging mechanisms that process user-controlled input without proper sanitization.
Business
The organization's infrastructure becomes a staging point for ransomware deployment or persistent backdoor installation across the network.
3
Lateral reach — past segmentation narrative 3
Attacker
I establish command and control channels to exfiltrate sensitive data or encrypt critical systems for extortion.
Business
The organization faces operational disruption, financial loss from ransom demands, regulatory penalties, and reputational damage from data breaches.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05
Coverage & confidence
— what we know, and what we don’tEstablished (cited)
Coverage gaps — stated, not hidden
Disclosure & credit2
Catalogued by apacheCNA
Credited with finding itNo finder is named in the public CVE record or the scanned vendor advisory — attribution scoped to the sources checked.
Found an error? Propose a correction.
A correction is a cited counter-claim — it must cite a source,
gets reviewed by a second human, and is never auto-applied. See the
correction convention and our identity
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