CVE-2021-45105

Apache Log4j2 does not always protect from infinite recursion in lookup evaluation

MEDIUM
5.9
CVSS Score
Published: December 18, 2021 at 11:55 AM UTC
Updated: August 25, 2026 at 04:28 PM UTC
121 products affected across 5 vendorsDebian LinuxE Business SuitePeopleSoft Enterprise PeopleTools

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Severity
MEDIUM5.9
Exploit prediction
EPSS 100%
SSVC
No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

2.0 ≤ v < 2.3.12.13.0 ≤ v ≤ 2.16.02.4 ≤ v < 2.12.3log4j-core ≤ v < 2.17.0log4j-core
Affected range stops below 2.12.3, so it looks safe — our inference, not a vendor statement
Affected range stops below 2.17.0, so it looks safe — our inference, not a vendor statement
Affected range stops below 2.3.1, so it looks safe — our inference, not a vendor statement
All versions

References (13)

Mailing Listx_refsource_MLISTMitigationThird Party Advisory
http://www.openwall.com/lists/oss-security/2021/12/19/1
x_refsource_CONFIRMx_refsource_MISCRelease NotesVendor Advisory
https://logging.apache.org/log4j/2.x/security.html
Vendor Advisoryx_refsource_DEBIANThird Party Advisory
https://www.debian.org/security/2021/dsa-5024

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.9MEDIUMCISA-ADP
Attack Vector
NETWORK
Complexity
HIGH
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-20CWE-674

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