Apache Log4j Core's Rfc5424Layout https://logging.apache.org/log4j/2.x/manual/layouts.html#RFC5424Layout , in versions 2.21.0 through 2.25.3, is vulnerable to log injection via CRLF sequences due to undocumented renames of security-relevant configuration attributes.
Two distinct issues affect users of stream-based syslog services who configure Rfc5424Layout directly:
* The newLineEscape attribute was silently renamed, causing newline escaping to stop working for users of TCP framing (RFC 6587), exposing them to CRLF injection in log output.
* The useTlsMessageFormat attribute was silently renamed, causing users of TLS framing (RFC 5425) to be silently downgraded to unframed TCP (RFC 6587), without newline escaping.
Users of the SyslogAppender are not affected, as its configuration attributes were not modified.
Users are advised to upgrade to Apache Log4j Core 2.25.4, which corrects this issue.
References
| Link | Resource |
|---|---|
| https://github.com/apache/logging-log4j2/pull/4074 | Issue Tracking Patch |
| https://lists.apache.org/thread/3k1clr2l6vkdnl4cbhjrnt1nyjvb5gwt | Mailing List Vendor Advisory |
| https://logging.apache.org/cyclonedx/vdr.xml | Product |
| https://logging.apache.org/log4j/2.x/manual/layouts.html#RFC5424Layout | Technical Description |
| https://logging.apache.org/security.html#CVE-2026-34478 | Vendor Advisory |
| http://www.openwall.com/lists/oss-security/2026/04/10/7 | Mailing List Third Party Advisory |
Configurations
Configuration 1 (hide)
|
History
24 Apr 2026, 18:10
| Type | Values Removed | Values Added |
|---|---|---|
| References | () https://github.com/apache/logging-log4j2/pull/4074 - Issue Tracking, Patch | |
| References | () https://lists.apache.org/thread/3k1clr2l6vkdnl4cbhjrnt1nyjvb5gwt - Mailing List, Vendor Advisory | |
| References | () https://logging.apache.org/cyclonedx/vdr.xml - Product | |
| References | () https://logging.apache.org/log4j/2.x/manual/layouts.html#RFC5424Layout - Technical Description | |
| References | () https://logging.apache.org/security.html#CVE-2026-34478 - Vendor Advisory | |
| References | () http://www.openwall.com/lists/oss-security/2026/04/10/7 - Mailing List, Third Party Advisory | |
| CPE | cpe:2.3:a:apache:log4j:3.0.0:beta3:*:*:*:*:*:* cpe:2.3:a:apache:log4j:3.0.0:beta1:*:*:*:*:*:* cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:* cpe:2.3:a:apache:log4j:3.0.0:beta2:*:*:*:*:*:* |
|
| First Time |
Apache log4j
Apache |
|
| CVSS |
v2 : v3 : |
v2 : unknown
v3 : 7.5 |
10 Apr 2026, 17:17
| Type | Values Removed | Values Added |
|---|---|---|
| References |
|
10 Apr 2026, 16:16
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-04-10 16:16
Updated : 2026-04-24 18:10
NVD link : CVE-2026-34478
Mitre link : CVE-2026-34478
CVE.ORG link : CVE-2026-34478
JSON object : View
Products Affected
apache
- log4j