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pkarwasz pushed a commit to branch fix/new-cves
in repository https://gitbox.apache.org/repos/asf/logging-site.git

commit 9b9866443c5699f2801d9ee6fd4aeaa3de2c007c
Author: Piotr P. Karwasz <[email protected]>
AuthorDate: Fri Apr 10 14:51:43 2026 +0200

    Add details for CVE-2026-40021
---
 .../modules/ROOT/pages/_vulnerabilities.adoc       | 41 ++++++++++++++++
 src/site/static/cyclonedx/vdr.xml                  | 55 ++++++++++++++++++++++
 2 files changed, 96 insertions(+)

diff --git a/src/site/antora/modules/ROOT/pages/_vulnerabilities.adoc 
b/src/site/antora/modules/ROOT/pages/_vulnerabilities.adoc
index 7f24d36f..69ffdcbe 100644
--- a/src/site/antora/modules/ROOT/pages/_vulnerabilities.adoc
+++ b/src/site/antora/modules/ROOT/pages/_vulnerabilities.adoc
@@ -29,6 +29,47 @@ Version ranges follow the 
https://github.com/package-url/vers-spec/blob/main/VER
 For brevity, mathematical interval notation is used, with the union operator 
(`∪`) to represent multiple ranges.
 ====
 
+[#CVE-2026-40021]
+== {cve-url-prefix}/CVE-2026-40021[CVE-2026-40021]
+
+[cols="1h,5"]
+|===
+|Summary |Silent log event loss in `XmlLayout` and `XmlLayoutSchemaLog4J` due 
to unescaped XML 1.0 forbidden characters
+|CVSS 4.x Score & Vector |6.3 MEDIUM 
(CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N)
+|Components affected |Log4net
+|Versions affected |`[0, 3.3.0)`
+|Versions fixed |`3.3.0`
+|===
+
+[#CVE-2026-40021-description]
+=== Description
+
+Apache Log4net's
+https://logging.apache.org/log4net/manual/configuration/layouts.html#layout-list[`XmlLayout`]
+and
+https://logging.apache.org/log4net/manual/configuration/layouts.html#layout-list[`XmlLayoutSchemaLog4J`],
+in versions before 3.3.0, fail to sanitize characters forbidden by the
+https://www.w3.org/TR/xml/#charsets[XML 1.0 specification]
+in MDC property keys and values, as well as the identity field that may carry 
attacker-influenced data.
+This causes an exception during serialization and the silent loss of the 
affected log event.
+
+An attacker who can influence any of these fields can exploit this to suppress 
individual log records, impairing audit trails and detection of malicious 
activity.
+
+[#CVE-2026-40021-remediation]
+=== Remediation
+
+Users are advised to upgrade to Apache Log4net version `3.3.0`, which fixes 
this issue.
+
+[#CVE-2026-40021-credits]
+=== Credits
+
+This issue was discovered by f00dat.
+
+[#CVE-2026-40021-references]
+=== References
+* {cve-url-prefix}/CVE-2026-40021[CVE-2026-40021]
+* https://github.com/apache/logging-log4net/pull/280[Pull request that fixes 
the issue]
+
 [#CVE-2026-34481]
 == {cve-url-prefix}/CVE-2026-34481[CVE-2026-34481]
 
diff --git a/src/site/static/cyclonedx/vdr.xml 
b/src/site/static/cyclonedx/vdr.xml
index dfa85701..ae0f4bb4 100644
--- a/src/site/static/cyclonedx/vdr.xml
+++ b/src/site/static/cyclonedx/vdr.xml
@@ -89,6 +89,61 @@
 
   <vulnerabilities>
 
+    <vulnerability>
+        <id>CVE-2026-40021</id>
+        <source>
+            <name>NVD</name>
+            <url>https://nvd.nist.gov/vuln/detail/CVE-2026-40021</url>
+        </source>
+        <ratings>
+            <rating>
+                <source>
+                    <name>The Apache Software Foundation</name>
+                    <url>
+                        
<![CDATA[https://www.first.org/cvss/calculator/4-0#CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N]]></url>
+                </source>
+                <score>6.3</score>
+                <severity>medium</severity>
+                <method>CVSSv4</method>
+                
<vector>AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N</vector>
+            </rating>
+        </ratings>
+        <cwes>
+            <cwe>116</cwe>
+        </cwes>
+        <description><![CDATA[Apache Log4net's
+https://logging.apache.org/log4net/manual/configuration/layouts.html#layout-list[`XmlLayout`]
+and
+https://logging.apache.org/log4net/manual/configuration/layouts.html#layout-list[`XmlLayoutSchemaLog4J`],
+in versions before 3.3.0, fail to sanitize characters forbidden by the
+https://www.w3.org/TR/xml/#charsets[XML 1.0 specification]
+in MDC property keys and values, as well as the identity field that may carry 
attacker-influenced data.
+This causes an exception during serialization and the silent loss of the 
affected log event.
+
+An attacker who can influence any of these fields can exploit this to suppress 
individual log records, impairing audit trails and detection of malicious 
activity.]]></description>
+        <recommendation><![CDATA[Users are advised to upgrade to Apache 
Log4net version `3.3.0`, which fixes this issue.]]></recommendation>
+        <created>2026-04-10T11:53:17Z</created>
+        <published>2026-04-10T11:53:17Z</published>
+        <updated>2026-04-10T11:53:17Z</updated>
+        <credits>
+            <individuals>
+                <individual>
+                    <name>f00dat</name>
+                </individual>
+            </individuals>
+        </credits>
+        <affects>
+            <target>
+                <ref>log4net</ref>
+                <versions>
+                    <version>
+                        <range><![CDATA[vers:nuget/>=0|<3.3.0]]></range>
+                    </version>
+                </versions>
+            </target>
+        </affects>
+    </vulnerability>
+
     <vulnerability>
         <id>CVE-2026-34481</id>
         <source>

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