Apache Log4cxx: Improper Output Neutralization for Logs
CVE-2025-54813 is a high-severity improper output neutralization for logs vulnerability in Apache Log4cxx from Apache, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 1.5.0 as the first without the flaw, so updating Apache Log4cxx to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 1.5% chance of exploitation within 30 days, higher than 75% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Apache Log4cxx to 1.5.0 or a later version.
- Update Log4cxx to 1.5.0 or a later version.
- Read the advisory on logging.apache.org for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Apache | Apache Log4cxx | 0.11.0 up to, but not including, 1.5.0 | 1.5.0 |
| Apache | Log4cxx | before 1.5.0 | 1.5.0 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- HighData or code can be modified at will.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 6.3 | Medium | CNA (apache.org) |
| CVSS 3.1 | 7.5 | High | NVD |
Official description
Improper Output Neutralization for Logs vulnerability in Apache Log4cxx. When using JSONLayout, not all payload bytes are properly escaped. If an attacker-supplied message contains certain non-printable characters, these will be passed along in the message and written out as part of the JSON message. This may prevent applications that consume these logs from correctly interpreting the information within them. This issue affects Apache Log4cxx: before 1.5.0. Users are recommended to upgrade to version 1.5.0, which fixes the issue.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Output Neutralization for Logs
The product constructs a log message from external input, but it does not neutralize or incorrectly neutralizes special elements when the message is written to a log file.
How developers prevent this class of flaw
- Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
More Improper Output Neutralization for Logs vulnerabilities (CWE-117)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- github.com/apache/logging-log4cxx/pull/512Issue Tracking
Other references
Other vulnerabilities in Apache Log4cxx
- 8.8 High severity
Recent Improper Output Neutralization for Logs vulnerabilities
- 9.8 Critical severity
- 8.1 High severity
- 7.2 High severity
- 8.6 High severity
- 9.8 Critical severity
- 9.8 Critical severity
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