CVE-2026-40021Published

Apache Log4net: Silent log event loss in XmlLayout and XmlLayoutSchemaLog4J due to unescaped XML 1.0 forbidden characters

cve-program · CVE-2026-40021

Published

log4net

NuGet

Original vendor version evidence · not evaluated as a NuGet range

{
                    "collectionURL": "https://www.nuget.org/packages",
                    "cpes": [
                        "cpe:2.3:a:apache:log4net:*:*:*:*:*:*:*:*"
                    ],
                    "defaultStatus": "unaffected",
                    "packageName": "log4net",
                    "packageURL": "pkg:nuget/log4net",
                    "product": "Apache Log4net",
                    "vendor": "Apache Software Foundation",
                    "versions": [
                        {
                            "lessThan": "3.3.0",
                            "status": "affected",
                            "version": "0",
                            "versionType": "nuget"
                        }
                    ]
                }

Original source record · Cite this exact observation · Complete original publisher JSON

euvd · EUVD-2026-21488

Published

EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.

Original publisher date fields

datePublished: Apr 10, 2026, 3:44:17 PM

dateUpdated: Apr 10, 2026, 5:35:01 PM

1 related source bulletins · separate from aliases

WID-SEC-W-2026-1054: Apache log4net: Schwachstelle ermöglicht Manipulation von Dateien

CVE-2026-40021

No normalized affected-package data is projected for this source revision. The original publisher record may contain additional product and version evidence; this does not establish that a package is unaffected.

Original source record · Cite this exact observation · Complete original publisher JSON

nvd · CVE-2026-40021

Published

NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.

Source analysis status: Analyzed

Weakness classifications: CWE-116

Original publisher date fields

published: 2026-04-10T16:16:32.420

lastModified: 2026-10-26T21:10:00.170

1 source CPE criteria · context only

cpe:2.3:a:apache:log4net:*:*:*:*:*:*:*:*

The original JSON retains the logical configuration operators, exclusions and version bounds.

Original source record · Cite this exact observation · Complete original publisher JSON

osv · GHSA-4f7c-pmjv-c25w

Published

log4net

NuGet

ECOSYSTEM · introduced 0 → fixed 3.3.0

27 explicitly affected versions

1.2.10, 1.2.11, 2.0.0, 2.0.1, 2.0.10, 2.0.11, 2.0.12, 2.0.13, 2.0.14, 2.0.15, 2.0.16, 2.0.17, 2.0.2, 2.0.3, 2.0.4, 2.0.5, 2.0.6, 2.0.7, 2.0.8, 2.0.9, 3.0.0, 3.0.1, 3.0.2, 3.0.3, 3.0.4, 3.1.0, 3.2.0

Original source record · Cite this exact observation · Complete original publisher JSON