CVE-2026-49844 in Apache Log4j API
Improper encoding of non-finite floating-point values during MapMessage JSON serialization in Apache Log4j API produces output that is not valid JSON. This issue affects Apache Log4j API versions 2.13.1 through 2.25.4 and version 2.26.0. The fix for CVE-2026-34481 did not...
Quick answer
Apache Software Foundation Apache Log4j API should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.
Who is affected
Affected versions
- Apache Log4j API 2.13.1 to before 2.25.5
- Apache Log4j API 2.26.0 to before 2.26.1
- Apache Log4j API 3.0.0-alpha1 through 3.0.0-beta2
Fixed versions
- Apache Log4j API 2.25.5 or 2.26.1
How to fix it
Update Apache Log4j API. The old API can write broken JSON logs when bad values are logged.
- Upgrade org.apache.logging.log4j:log4j-api to Apache Log4j API 2.25.5 or 2.26.1.
- Rebuild and redeploy the app.
- Check log pipeline parsing after release.
- Block old Log4j API versions in dependency checks.
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Verify the fix
- Check the dependency tree and confirm org.apache.logging.log4j:log4j-api is fixed.
- Scan again and confirm CVE-2026-49844 is gone.
Related categories
Trusted references
FAQ
What is affected by CVE-2026-49844?
Apache Software Foundation Apache Log4j API versions listed as affected should be reviewed: Apache Log4j API 2.13.1 to before 2.25.5, Apache Log4j API 2.26.0 to before 2.26.1, Apache Log4j API 3.0.0-alpha1 through 3.0.0-beta2.
What should I fix first?
Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.
How do I confirm the fix worked?
Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.
How are Fixnx security risk categories chosen?
Fixnx keeps one canonical risk page and assigns only broad, relevant categories such as ecosystem, technology area, or vulnerability class.