Logback allows an attacker to instantiate classes already present on the class path

Description

ACE vulnerability in configuration file processing by QOS.CH logback-core up to and including version 1.5.24 in Java applications, allows an attacker to instantiate classes already present on the class path by compromising an existing logback configuration file.

The instantiation of a potentially malicious Java class requires that said class is present on the user's class-path. In addition, the attacker must have write access to a configuration file. However, after successful instantiation, the instance is very likely to be discarded with no further ado.

Basic information

Type
reviewed
Severity
low
Advisory on GitHub
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Repository advisory
Source code
Browse source ↗
Published (advisory)
2026-01-22 12:31:22 UTC
Updated
2026-01-22 18:06:44 UTC
GitHub reviewed
2026-01-22 18:06:44 UTC
NVD published
2026-01-22

EPSS Score

Score Percentile
0.01% 1.65%

CVSS Scores

Base score Version Severity Vector
1.8 4.0
CVSS:4.0/AV:L/AC:H/AT:P/PR:H/UI:N/VC:L/VI:L/VA:L/SC:L/SI:L/SA:L Click to expand
Attack vector (AV:L)
Attacker needs local access on the target system.
Attack complexity (AC:H)
Exploitation depends on constrained or hard-to-reproduce conditions.
Attack requirements (AT:P)
Additional preconditions must be present for exploitation.
Privileges required (PR:H)
High privileges are required.
User interaction (UI:N)
No user interaction is required.
Vulnerable system confidentiality impact (VC:L)
Limited confidentiality impact on the vulnerable system.
Vulnerable system integrity impact (VI:L)
Limited integrity impact on the vulnerable system.
Vulnerable system availability impact (VA:L)
Limited availability impact on the vulnerable system.
Subsequent system confidentiality impact (SC:L)
Limited confidentiality impact on subsequent systems.
Subsequent system integrity impact (SI:L)
Limited integrity impact on subsequent systems.
Subsequent system availability impact (SA:L)
Limited availability impact on subsequent systems.

Identifiers

CWEs

CWE id Name
CWE-20 Improper Input Validation

Affected packages (1)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
maven ch.qos.logback:logback-core < 1.5.25 1.5.25

References

cvelogic Threat Intelligence