Staging Environment: Content and features may be unstable or change without notice.
Advisory details: github_osv / GHSA-445c-vh5m-36rj
Advisory ID github_osv/GHSA-445c-vh5m-36rj
Aliases CVE-2026-34478
Summary Apache Log4j Core: log injection in `Rfc5424Layout` due to silent configuration incompatibility 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.
Status Published
Exploitability 0.5
Weighted Severity 6.2
Risk 3.1
Affected and Fixed Packages Package Details
Introduced and Fixed Package Commit Patches Package Commit Patches Details
Weaknesses (2)
CWE-117 Improper Output Neutralization for Logs
CWE-684 Incorrect Provision of Specified Functionality
System Score Found at
cvssv4 6.9 https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-445c-vh5m-36rj/GHSA-445c-vh5m-36rj.json
generic_textual MODERATE
Reference id Reference type URL
https://github.com/apache/logging-log4j2
https://logging.apache.org/cyclonedx/vdr.xml
http://www.openwall.com/lists/oss-security/2026/04/10/7
3k1clr2l6vkdnl4cbhjrnt1nyjvb5gwt Advisory https://lists.apache.org/thread/3k1clr2l6vkdnl4cbhjrnt1nyjvb5gwt
4074 Other https://github.com/apache/logging-log4j2/pull/4074
CVE-2026-34478 https://nvd.nist.gov/vuln/detail/CVE-2026-34478
layouts.html#RFC5424Layout Other https://logging.apache.org/log4j/2.x/manual/layouts.html#RFC5424Layout
security.html#CVE-2026-34478 Advisory https://logging.apache.org/security.html#CVE-2026-34478
No exploits are available.

No EPSS data available for this advisory.

Patch URL
There are no known patches.
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N Found at https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-445c-vh5m-36rj/GHSA-445c-vh5m-36rj.json
Attack Vector (AV) Attack Complexity (AC) Attack Requirements (AT) Privileges Required (PR) User Interaction (UI) Vulnerable System Impact Confidentiality (VC) Vulnerable System Impact Integrity (VI) Vulnerable System Impact Availability (VA) Subsequent System Impact Confidentiality (SC) Subsequent System Impact Integrity (SI) Subsequent System Impact Availability (SA)

network

adjacent

local

physical

low

high

none

present

none

low

high

none

passive

active

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none

Vector: SSVCv2/E:N/A:Y/T:P/P:M/B:A/M:M/D:T/2026-04-10T17:48:27Z/

Decision: Track

Source URL: https://github.com/cisagov/vulnrichment/blob/develop/2026/34xxx/CVE-2026-34478.json

Source Advisory: vulnrichment/CVE-2026-34478

View SSVC decision tree 
[{'Exploitation': 'none'},
 {'Automatable': 'yes'},
 {'Technical Impact': 'partial'},
 {'Mission Prevalence': 'minimal'},
 {'Public Well-being Impact': 'material'},
 {'Mission & Well-being': 'medium'}]