CVE-2025-54812VulnerabilityPublished 22 Aug 2025Updated 4 Nov 2025

CVE-2025-54812: Apache Log4cxx · Log Injection

Affects Apache Log4cxxSource CVE Database V5

Not known to be exploited · CVSS 2.1 Low · fixed in 1.5.0 : update Apache Log4cxx when convenient.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 4.0 base score

2.1Low

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 1.2% chance of exploitation in 30 days – higher than 68% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.5.0

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

Attack Vector: Network
Attack Complexity: High
Attack Requirements: None
Privileges Required: None
User Interaction: Active
Vulnerable system confidentiality: Low
Vulnerable system integrity: Low
Vulnerable system availability: None
Subsequent system confidentiality: Low
Subsequent system integrity: Low
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: High: The successful attack depends on the evasion or circumvention of security-enhancing techniques in place that would otherwise hinder the attack. These include: Evasion of exploit mitigation techniques, for example, circumvention of address space randomization (ASLR) or data execution prevention (DEP) must be performed for the attack to be successful; Obtaining target-specific secrets. The attacker must gather some target-specific secret before the attack can be successful. A secret is any piece of information that cannot be obtained through any amount of reconnaissance. To obtain the secret the attacker must perform additional attacks or break otherwise secure measures (e.g. knowledge of a secret key may be needed to break a crypto channel). This operation must be performed for each attacked target.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: Active: Successful exploitation of this vulnerability requires a targeted user to perform specific, conscious interactions with the vulnerable system and the attacker’s payload, or the user’s interactions would actively subvert protection mechanisms which would lead to exploitation of the vulnerability.
Vulnerable system confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Vulnerable System.
Vulnerable system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Subsequent System.
Subsequent system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Subsequent System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 22 Aug 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Apache Software Foundation Apache Log4cxx	Affected =0	Fixed in–

AI-suggested

1. Upgrade Apache Log4cxx to version 1.5.0 or later, where the vulnerability is fixed by proper escaping of logger names in HTMLLayout. 2. Avoid using HTMLLayout for logging if possible, especially if untrusted input might influence logger names. 3. Ensure logger names are static and controlled by the application, never derived from user input or untrusted sources. 4. Implement strict input validation and sanitization on any data that could influence logger names or other log metadata. 5. Educate users and administrators to avoid opening HTML log files from untrusted sources or environments. 6. Consider alternative logging formats (e.g., plain text or JSON) that do not render in browsers or execute scripts. 7. Monitor logs for suspicious entries that could indicate attempts to inject malicious content. 8. Apply principle of least privilege to limit who can configure logging and access log files. 9. Integrate log integrity verification mechanisms to detect tampering. 10. Regularly review and audit logging configurations and practices to ensure compliance with security policies.

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.

Impact

For European organizations, the impact of CVE-2025-54812 is generally low but context-dependent. Organizations that generate HTML logs using Apache Log4cxx with HTMLLayout and allow untrusted input to influence logger names are at risk of XSS attacks when logs are viewed in browsers. This could lead to misleading log information, concealment of malicious activity, or theft of sensitive data from users viewing the logs. While the direct impact on confidentiality, integrity, and availability is limited, the vulnerability could aid attackers in covering tracks or conducting social engineering attacks via malicious log content. Critical sectors such as finance, healthcare, and government that rely on detailed logging for auditing and compliance may find such manipulation problematic. However, since exploitation requires user interaction and specific configuration, the overall risk remains low. European organizations should assess their use of Log4cxx, especially in environments where HTML logs are generated and viewed, to determine exposure.

Summary

CVE-2025-54812 is a vulnerability classified under CWE-117 (Improper Output Neutralization for Logs) found in Apache Log4cxx versions prior to 1.5.0. The issue arises specifically when the logging framework is configured to use the HTMLLayout, which formats log entries as HTML files. In this scenario, logger names are not properly escaped before being written into the HTML log output. If an attacker can influence or control the logger name—typically a string used to identify the source of log messages—they can inject malicious HTML or JavaScript code into the log file. When a user subsequently opens this HTML log file in a web browser, the injected script can execute, resulting in a cross-site scripting (XSS) attack. This could allow attackers to hide log entries, manipulate log content, or potentially steal sensitive information from the user viewing the logs. However, exploitation requires several conditions: the use of HTMLLayout, logger names derived from untrusted input, and user interaction to open the HTML log file. Logger names are generally static and controlled by developers, limiting the attack surface. The vulnerability has a CVSS 4.0 base score of 2.1, reflecting low severity due to the complexity and limited impact. The issue is resolved in Apache Log4cxx version 1.5.0, which properly escapes logger names in HTMLLayout outputs.

CWE-117Improper Output Neutralization for Logs (opens in a new tab)
Base weaknessLikelihood of exploit: MediumOWASP Top 10 A09:2025: Security Logging & Alerting Failures (opens in a new tab)
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.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
Implementation · Output Encoding
Use and specify an output encoding that can be handled by the downstream component that is reading the output. Common encodings include ISO-8859-1, UTF-7, and UTF-8.
Implementation · Input Validation
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).
OWASP Cheat Sheets
Logging (opens in a new tab)
Content Security Policy (opens in a new tab)
Application Logging Vocabulary (opens in a new tab)
OWASP ASVS 4.0.3
V7.3.1 (opens in a new tab)
V14.4.6 (opens in a new tab)
V14.4.4 (opens in a new tab)
Attack patterns
Audit Log Manipulation (opens in a new tab)
Web Server Logs Tampering (opens in a new tab)
Log Injection-Tampering-Forging (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 10 Nov 2025, 19:08 UTC

WeaknessesCWE-117

Technical details

References

Community reviews

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