Signal is active with 1 mentions in latest observed window
Recommended action window: Monitor and triage in normal cycle
NVD description
The Log4j1XmlLayout from the Apache Log4j 1-to-Log4j 2 bridge fails to escape characters forbidden by the XML 1.0 standard, producing malformed XML output. Conforming XML parsers are required to reject documents containing such characters with a fatal error, which may cause downstream log processing systems to drop or fail to index affected records. Two groups of users are affected: * Those using Log4j1XmlLayout directly in a Log4j Core 2 configuration file. * Those using the Log4j 1 configuration compatibility layer with org.apache.log4j.xml.XMLLayout specified as the layout class. Users are advised to upgrade to Apache Log4j 1-to-Log4j 2 bridge version 2.25.4, which corrects this issue. Note: The Apache Log4j 1-to-Log4j 2 bridge is deprecated and will not be present in Log4j 3. Users are encouraged to consult the Log4j 1 to Log4j 2 migration guide https://logging.apache.org/log4j/2.x/migrate-from-log4j1.html , and specifically the section on eliminating reliance on the bridge.
Priority
LOW
Exploitation
NONE
PoC
YES
Patch
AVAILABLE
Momentum
NONE
If you run products in this scope, you should treat this CVE as relevant to your environment.
1 version affected across 1 product
CVE-2026-34479 The Log4j1XmlLayout from the Apache Log4j 1-to-Log4j 2 bridge fails to escape characters forbidden by the XML 1.0 standard, producing malformed XML output. Conforming… https://www.cve.org/CVERecord?id=CVE-2026-34479
Post summary
A new flaw in the Apache Log4j 1-to-Log4j 2 bridge’s Log4j1XmlLayout causes malformed XML by not escaping forbidden characters, but no patches, PoCs, or exploitation activity are reported.
6 of 6 entries
| Part | Vendor | Product | Version | Target SW | Target HW |
|---|---|---|---|---|---|
| App | apache | log4j | - | - | - |
| App | apache | log4j | 3.0.0 | - | - |
| App | apache | log4j | 3.0.0 | - | - |
| App | apache | log4j | 3.0.0 | - | - |
| App | apache | log4j | 3.0.0 | - | - |
| App | apache | log4j | 3.0.0 | - | - |