Advisory details:
gitlab / maven/org.apache.logging.log4j/log4j-core/CVE-2026-34479
| Advisory ID | gitlab/maven/org.apache.logging.log4j/log4j-core/CVE-2026-34479 |
| Aliases |
CVE-2026-34479
GHSA-h383-gmxw-35v2 |
| Summary | Apache Log4j 1 to Log4j 2 bridge: silent log event loss in Log4j1XmlLayout due to unescaped XML 1.0 forbidden characters 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. |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 0.0 |
| Risk | |
| Affected and Fixed Packages | Package Details |
| Introduced and Fixed Package Commit Patches | Package Commit Patches Details |
| System | Score | Found at |
|---|---|---|
| cvssv3.1 | https://gitlab.com/gitlab-org/advisories-community/-/blob/main/maven/org.apache.logging.log4j/log4j-core/CVE-2026-34479.yml |
| Reference id | Reference type | URL |
|---|---|---|
| https://logging.apache.org/cyclonedx/vdr.xml | ||
| 4078 | Other | https://github.com/apache/logging-log4j2/pull/4078 |
| CVE-2026-34479 | https://nvd.nist.gov/vuln/detail/CVE-2026-34479 | |
| gd0hp6mj17rn3kj279vgy4p7kd4zz5on | Advisory | https://lists.apache.org/thread/gd0hp6mj17rn3kj279vgy4p7kd4zz5on |
| GHSA-h383-gmxw-35v2 | https://github.com/advisories/GHSA-h383-gmxw-35v2 | |
| migrate-from-log4j1.html | Other | https://logging.apache.org/log4j/2.x/migrate-from-log4j1.html |
| security.html#CVE-2026-34479 | Advisory | https://logging.apache.org/security.html#CVE-2026-34479 |
No EPSS data available for this advisory.
| Patch URL | |
|---|---|
| There are no known patches. | |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
There are no SSVC decisions available.