CVE-2026-105240: Software Security Vulnerability Vulnerability

MODERATE
Advisory Identifier: GHSA-q2xj-998m-58gf
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CVSS 5.3
CWE-158
Published
Advisory Summary

CVE-2026-105240 is a MODERATE (CVSS 5.3) security vulnerability vulnerability (CWE-158: Improper Neutralization of Null Byte or NUL Character) affecting Software libraries in the Maven ecosystem. The weakness occurs when the product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes nul characters or null bytes when they are sent to a downstream component.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-105240 at a Glance

CVE Identifier CVE-2026-105240
GHSA Identifier GHSA-q2xj-998m-58gf
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-158: Improper Neutralization of Null Byte or NUL Character
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 5.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-105240

To remediate this vulnerability, upgrade all affected Software dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-105240, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree

Analyze the terminal output to locate any version of Software in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The mvn dependency:tree command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-158: Improper Neutralization of Null Byte or NUL Character, where the product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes nul characters or null bytes when they are sent to a downstream component. In Software, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

Improper Neutralization of Null Byte or NUL Character vulnerability in the OutputDebugStringAppender of Apache log4net. A NUL character in logged content ended the debug output record at that point, so everything the layout rendered after it, including exception text and trailing fields, was silently lost. A party whose data reaches a log message could hide the rest of that record. Only applications on Windows that use OutputDebugStringAppender are affected. This issue affects Apache log4net: from 1.2.9 before 3.5.0. Users are recommended to upgrade to version 3.5.0, which fixes the issue.

References

NVD — CVE-2026-105240 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-105240
Software Source Repository REPOSITORY
https://github.com/apache/logging-log4net/pull/315
Security Fix Commit FIX COMMIT
https://github.com/apache/logging-log4net/commit/6046fe9d7f353b49fe995361c071ec2eea8f7ef6
lists.apache.org/thread.html/gyw2d4p... WEB
https://lists.apache.org/thread.html/gyw2d4ppy82t1vlpdknkfd1nmzp21z17
Software Security Information SECURITY
http://www.openwall.com/lists/oss-security/2026/10/07/18

Frequently Asked Questions

What is CVE-2026-105240?
CVE-2026-105240 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-158: Improper Neutralization of Null Byte or NUL Character.
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-105240?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2026-105240?
CVE-2026-105240 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.
What CWE is associated with CVE-2026-105240?
CVE-2026-105240 is classified under CWE-158: Improper Neutralization of Null Byte or NUL Character (The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes NUL characters or null bytes when they are sent to a downstream component.).
How can I check Maven dependencies for CVE-2026-105240?
Run the dependency tree command: 'mvn dependency:tree'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-q2xj-998m-58gf",
  "modified" : "2026-10-07T09:32:18Z",
  "published" : "2026-10-06T21:31:59Z",
  "aliases" : [ "CVE-2026-105240" ],
  "details" : "Improper Neutralization of Null Byte or NUL Character vulnerability in the OutputDebugStringAppender of Apache log4net.\n\nA NUL character in logged content ended the debug output record at that point, so everything the layout rendered after it, including exception text and trailing fields, was silently lost. A party whose data reaches a log message could hide the rest of that record. Only applications on Windows that use OutputDebugStringAppender are affected.\n\nThis issue affects Apache log4net: from 1.2.9 before 3.5.0.\n\nUsers are recommended to upgrade to version 3.5.0, which fixes the issue.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-105240"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/apache/logging-log4net/pull/315"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/apache/logging-log4net/commit/6046fe9d7f353b49fe995361c071ec2eea8f7ef6"
  }, {
    "type" : "WEB",
    "url" : "https://lists.apache.org/thread.html/gyw2d4ppy82t1vlpdknkfd1nmzp21z17"
  }, {
    "type" : "WEB",
    "url" : "http://www.openwall.com/lists/oss-security/2026/10/07/18"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-158" ],
    "severity" : "MODERATE",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-10-06T20:17:15Z"
  }
}