Vulnerability

CVE-2021-45105

Medium· 5.9CVSS5.9EPSS74%

.rules3/5

Apache Log4j2 vulnerable to Improper Input Validation and Uncontrolled Recursion

Apache Log4j2 versions 2.0-alpha1 through 2.16.0 (excluding 2.12.3) 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 and 2.12.3. # Affected packages Only the `org.apache.logging.log4j:log4j-core` package is directly affected by this vulnerability. The `org.apache.logging.log4j:log4j-api` should be kept at the same version as the `org.apache.logging.log4j:log4j-core` package to ensure compatability if in use.

Threat signal

70/100

High

Severity

medium

CVSS

5.9

EPSS

74%

Active

CVSS

v3.1via NVDOpen in FIRST calculator →

5.9/ 10MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack VectorNetworkExploitable remotely over the internet — no local access needed.
Attack ComplexityHighRequires conditions outside attacker's control (race, brute-force, configuration
Privileges RequiredNoneUnauthenticated — no credentials needed.
User InteractionNoneFully automated — no victim action needed.
ScopeUnchangedImpact contained to the vulnerable component.
Confidentiality ImpactNoneNo confidentiality impact.
Integrity ImpactNoneNo integrity impact.
Availability ImpactHighTotal loss of availability — full DoS possible.

EPSS

Exploit prediction · 30-day horizonFIRST.org →

74.0%

probability of exploitation in next 30 days

p99

higher than 99% of all CVEs

3-day trend↑ 0pp

Statistically about to be weaponized — top-tier triage urgency.

Vendor VEX

No VEX statements published for CVE-2021-45105. Vendors publish VEX (Vulnerability Exploitability eXchange) to assert per-product whether a CVE is actually exploitable in their distribution.

SSVCDefer

No exploitation, limited impact or prevalence

exploitation: none
automatable: no
impact: partial
mission: support

Lifecycle

2021-12-18Published
2021-12-23Vendor advisory · amazon-linuxALAS2-2021-1733 — ALAS2-2021-1733 (medium): aws-kinesis-agent
2026-05-29Last modified2 sources

Entity graph

2 nodes · 1 edges · click to pivot

CVEActorVendor advisoryIOCNews

Vendor advisories

amazon-linuxALAS2-2021-1733ALAS2-2021-1733 (medium): aws-kinesis-agent

Mentions in news & research

research:snykLog4j 2.16 High Severity Vulnerability (CVE-2021-45105) Discovered2021-12-18

References

No source-event history recorded yet. New revisions will appear here as ingestors re-fetch this CVE.