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8 vulnerabilities found for Apache Log4j Core by Apache Software Foundation

CVE-2026-34480 (GCVE-0-2026-34480)

Vulnerability from nvd – Published: 2026-04-10 15:42 – Updated: 2026-04-10 17:45
VLAI?
Title
Apache Log4j Core: Silent log event loss in XmlLayout due to unescaped XML 1.0 forbidden characters
Summary
Apache Log4j Core's XmlLayout https://logging.apache.org/log4j/2.x/manual/layouts.html#XmlLayout , in versions up to and including 2.25.3, fails to sanitize characters forbidden by the XML 1.0 specification https://www.w3.org/TR/xml/#charsets producing invalid XML output whenever a log message or MDC value contains such characters. The impact depends on the StAX implementation in use: * JRE built-in StAX: Forbidden characters are silently written to the output, producing malformed XML. Conforming parsers must reject such documents with a fatal error, which may cause downstream log-processing systems to drop the affected records. * Alternative StAX implementations (e.g., Woodstox https://github.com/FasterXML/woodstox , a transitive dependency of the Jackson XML Dataformat module): An exception is thrown during the logging call, and the log event is never delivered to its intended appender, only to Log4j's internal status logger. Users are advised to upgrade to Apache Log4j Core 2.25.4, which corrects this issue by sanitizing forbidden characters before XML output.
Severity ?
6.9 (Medium)
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
CWE
  • CWE-116 - Improper Encoding or Escaping of Output
Assigner
References
Impacted products
Vendor Product Version
Apache Software Foundation Apache Log4j Core Affected: 2.0-alpha1 , < 2.25.4 (maven)
Affected: 3.0.0-alpha1 , ≤ 3.0.0-beta3 (maven)
    cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*
 Create a notification for this product.
Credits
Ap4sh (Samy Medjahed) and Ethicxz (Eliott Laurie) (original reporters) jabaltarik1 (independently)
Show details on NVD website
To clipboard 

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CVE-2026-34478 (GCVE-0-2026-34478)

Vulnerability from nvd – Published: 2026-04-10 15:40 – Updated: 2026-04-10 17:50
VLAI?
Title
Apache Log4j Core: Log injection in Rfc5424Layout due to silent configuration incompatibility
Summary
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.
Severity ?
6.9 (Medium)
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
CWE
  • CWE-684 - Incorrect Provision of Specified Functionality
  • CWE-117 - Improper Output Neutralization for Logs
Assigner
References
Impacted products
Vendor Product Version
Apache Software Foundation Apache Log4j Core Affected: 2.21.0 , < 2.25.4 (maven)
Affected: 3.0.0-beta1 , ≤ 3.0.0-beta3 (maven)
    cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*
 Create a notification for this product.
Credits
Samuli Leinonen
Show details on NVD website
To clipboard 

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CVE-2026-34477 (GCVE-0-2026-34477)

Vulnerability from nvd – Published: 2026-04-10 15:36 – Updated: 2026-04-10 17:38
VLAI?
Title
Apache Log4j Core: verifyHostName attribute silently ignored in TLS configuration, allowing hostname verification bypass
Summary
The fix for CVE-2025-68161 https://logging.apache.org/security.html#CVE-2025-68161 was incomplete: it addressed hostname verification only when enabled via the log4j2.sslVerifyHostName https://logging.apache.org/log4j/2.x/manual/systemproperties.html#log4j2.sslVerifyHostName system property, but not when configured through the verifyHostName https://logging.apache.org/log4j/2.x/manual/appenders/network.html#SslConfiguration-attr-verifyHostName attribute of the <Ssl> element. Although the verifyHostName configuration attribute was introduced in Log4j Core 2.12.0, it was silently ignored in all versions through 2.25.3, leaving TLS connections vulnerable to interception regardless of the configured value. A network-based attacker may be able to perform a man-in-the-middle attack when all of the following conditions are met: * An SMTP, Socket, or Syslog appender is in use. * TLS is configured via a nested <Ssl> element. * The attacker can present a certificate issued by a CA trusted by the appender's configured trust store, or by the default Java trust store if none is configured. This issue does not affect users of the HTTP appender, which uses a separate verifyHostname https://logging.apache.org/log4j/2.x/manual/appenders/network.html#HttpAppender-attr-verifyHostName attribute that was not subject to this bug and verifies host names by default. Users are advised to upgrade to Apache Log4j Core 2.25.4, which corrects this issue.
Severity ?
6.3 (Medium)
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:L/SA:N
CWE
  • CWE-297 - Improper Validation of Certificate with Host Mismatch
Assigner
References
Impacted products
Vendor Product Version
Apache Software Foundation Apache Log4j Core Affected: 2.12.0 , < 2.25.4 (maven)
Affected: 3.0.0-alpha1 , ≤ 3.0.0-beta3 (maven)
    cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*
 Create a notification for this product.
Credits
Samuli Leinonen (original reporter) Naresh Kandula (independently) Vitaly Simonovich (independently) Raijuna (independently) Danish Siddiqui (djvirus, independently) Markus Magnuson (independently) Haruki Oyama (Waseda University, independently)
Show details on NVD website
To clipboard 

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CVE-2025-68161 (GCVE-0-2025-68161)

Vulnerability from nvd – Published: 2025-12-18 20:47 – Updated: 2026-04-10 16:18
VLAI?
Title
Apache Log4j Core: Missing TLS hostname verification in Socket appender
Summary
The Socket Appender in Apache Log4j Core versions 2.0-beta9 through 2.25.2 does not perform TLS hostname verification of the peer certificate, even when the verifyHostName https://logging.apache.org/log4j/2.x/manual/appenders/network.html#SslConfiguration-attr-verifyHostName configuration attribute or the log4j2.sslVerifyHostName https://logging.apache.org/log4j/2.x/manual/systemproperties.html#log4j2.sslVerifyHostName system property is set to true. This issue may allow a man-in-the-middle attacker to intercept or redirect log traffic under the following conditions: * The attacker is able to intercept or redirect network traffic between the client and the log receiver. * The attacker can present a server certificate issued by a certification authority trusted by the Socket Appender’s configured trust store (or by the default Java trust store if no custom trust store is configured). Users are advised to upgrade to Apache Log4j Core version 2.25.3, which addresses this issue. As an alternative mitigation, the Socket Appender may be configured to use a private or restricted trust root to limit the set of trusted certificates.
Severity ?
6.3 (Medium)
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:L/SA:N
CWE
  • CWE-297 - Improper Validation of Certificate with Host Mismatch
Assigner
References
Impacted products
Vendor Product Version
Apache Software Foundation Apache Log4j Core Affected: 2.0-beta9 , < 2.25.3 (maven)
Affected: 3.0.0-alpha1 , ≤ 3.0.0-beta3 (maven)
    cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*
 Create a notification for this product.
Credits
Samuli Leinonen
Show details on NVD website
To clipboard 

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CVE-2026-34480 (GCVE-0-2026-34480)

Vulnerability from cvelistv5 – Published: 2026-04-10 15:42 – Updated: 2026-04-10 17:45
VLAI?
Title
Apache Log4j Core: Silent log event loss in XmlLayout due to unescaped XML 1.0 forbidden characters
Summary
Apache Log4j Core's XmlLayout https://logging.apache.org/log4j/2.x/manual/layouts.html#XmlLayout , in versions up to and including 2.25.3, fails to sanitize characters forbidden by the XML 1.0 specification https://www.w3.org/TR/xml/#charsets producing invalid XML output whenever a log message or MDC value contains such characters. The impact depends on the StAX implementation in use: * JRE built-in StAX: Forbidden characters are silently written to the output, producing malformed XML. Conforming parsers must reject such documents with a fatal error, which may cause downstream log-processing systems to drop the affected records. * Alternative StAX implementations (e.g., Woodstox https://github.com/FasterXML/woodstox , a transitive dependency of the Jackson XML Dataformat module): An exception is thrown during the logging call, and the log event is never delivered to its intended appender, only to Log4j's internal status logger. Users are advised to upgrade to Apache Log4j Core 2.25.4, which corrects this issue by sanitizing forbidden characters before XML output.
Severity ?
6.9 (Medium)
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
CWE
  • CWE-116 - Improper Encoding or Escaping of Output
Assigner
References
Impacted products
Vendor Product Version
Apache Software Foundation Apache Log4j Core Affected: 2.0-alpha1 , < 2.25.4 (maven)
Affected: 3.0.0-alpha1 , ≤ 3.0.0-beta3 (maven)
    cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*
 Create a notification for this product.
Credits
Ap4sh (Samy Medjahed) and Ethicxz (Eliott Laurie) (original reporters) jabaltarik1 (independently)
Show details on NVD website
To clipboard 

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CVE-2026-34478 (GCVE-0-2026-34478)

Vulnerability from cvelistv5 – Published: 2026-04-10 15:40 – Updated: 2026-04-10 17:50
VLAI?
Title
Apache Log4j Core: Log injection in Rfc5424Layout due to silent configuration incompatibility
Summary
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.
Severity ?
6.9 (Medium)
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
CWE
  • CWE-684 - Incorrect Provision of Specified Functionality
  • CWE-117 - Improper Output Neutralization for Logs
Assigner
References
Impacted products
Vendor Product Version
Apache Software Foundation Apache Log4j Core Affected: 2.21.0 , < 2.25.4 (maven)
Affected: 3.0.0-beta1 , ≤ 3.0.0-beta3 (maven)
    cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*
 Create a notification for this product.
Credits
Samuli Leinonen
Show details on NVD website
To clipboard 

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CVE-2026-34477 (GCVE-0-2026-34477)

Vulnerability from cvelistv5 – Published: 2026-04-10 15:36 – Updated: 2026-04-10 17:38
VLAI?
Title
Apache Log4j Core: verifyHostName attribute silently ignored in TLS configuration, allowing hostname verification bypass
Summary
The fix for CVE-2025-68161 https://logging.apache.org/security.html#CVE-2025-68161 was incomplete: it addressed hostname verification only when enabled via the log4j2.sslVerifyHostName https://logging.apache.org/log4j/2.x/manual/systemproperties.html#log4j2.sslVerifyHostName system property, but not when configured through the verifyHostName https://logging.apache.org/log4j/2.x/manual/appenders/network.html#SslConfiguration-attr-verifyHostName attribute of the <Ssl> element. Although the verifyHostName configuration attribute was introduced in Log4j Core 2.12.0, it was silently ignored in all versions through 2.25.3, leaving TLS connections vulnerable to interception regardless of the configured value. A network-based attacker may be able to perform a man-in-the-middle attack when all of the following conditions are met: * An SMTP, Socket, or Syslog appender is in use. * TLS is configured via a nested <Ssl> element. * The attacker can present a certificate issued by a CA trusted by the appender's configured trust store, or by the default Java trust store if none is configured. This issue does not affect users of the HTTP appender, which uses a separate verifyHostname https://logging.apache.org/log4j/2.x/manual/appenders/network.html#HttpAppender-attr-verifyHostName attribute that was not subject to this bug and verifies host names by default. Users are advised to upgrade to Apache Log4j Core 2.25.4, which corrects this issue.
Severity ?
6.3 (Medium)
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:L/SA:N
CWE
  • CWE-297 - Improper Validation of Certificate with Host Mismatch
Assigner
References
Impacted products
Vendor Product Version
Apache Software Foundation Apache Log4j Core Affected: 2.12.0 , < 2.25.4 (maven)
Affected: 3.0.0-alpha1 , ≤ 3.0.0-beta3 (maven)
    cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*
 Create a notification for this product.
Credits
Samuli Leinonen (original reporter) Naresh Kandula (independently) Vitaly Simonovich (independently) Raijuna (independently) Danish Siddiqui (djvirus, independently) Markus Magnuson (independently) Haruki Oyama (Waseda University, independently)
Show details on NVD website
To clipboard 

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CVE-2025-68161 (GCVE-0-2025-68161)

Vulnerability from cvelistv5 – Published: 2025-12-18 20:47 – Updated: 2026-04-10 16:18
VLAI?
Title
Apache Log4j Core: Missing TLS hostname verification in Socket appender
Summary
The Socket Appender in Apache Log4j Core versions 2.0-beta9 through 2.25.2 does not perform TLS hostname verification of the peer certificate, even when the verifyHostName https://logging.apache.org/log4j/2.x/manual/appenders/network.html#SslConfiguration-attr-verifyHostName configuration attribute or the log4j2.sslVerifyHostName https://logging.apache.org/log4j/2.x/manual/systemproperties.html#log4j2.sslVerifyHostName system property is set to true. This issue may allow a man-in-the-middle attacker to intercept or redirect log traffic under the following conditions: * The attacker is able to intercept or redirect network traffic between the client and the log receiver. * The attacker can present a server certificate issued by a certification authority trusted by the Socket Appender’s configured trust store (or by the default Java trust store if no custom trust store is configured). Users are advised to upgrade to Apache Log4j Core version 2.25.3, which addresses this issue. As an alternative mitigation, the Socket Appender may be configured to use a private or restricted trust root to limit the set of trusted certificates.
Severity ?
6.3 (Medium)
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:L/SA:N
CWE
  • CWE-297 - Improper Validation of Certificate with Host Mismatch
Assigner
References
Impacted products
Vendor Product Version
Apache Software Foundation Apache Log4j Core Affected: 2.0-beta9 , < 2.25.3 (maven)
Affected: 3.0.0-alpha1 , ≤ 3.0.0-beta3 (maven)
    cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*
 Create a notification for this product.
Credits
Samuli Leinonen
Show details on NVD website
To clipboard 

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      "title": "Apache Log4j Core: Missing TLS hostname verification in Socket appender",
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        "engine": "Vulnogram 0.2.0"
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  },
  "cveMetadata": {
    "assignerOrgId": "f0158376-9dc2-43b6-827c-5f631a4d8d09",
    "assignerShortName": "apache",
    "cveId": "CVE-2025-68161",
    "datePublished": "2025-12-18T20:47:49.123Z",
    "dateReserved": "2025-12-16T11:30:53.875Z",
    "dateUpdated": "2026-04-10T16:18:50.424Z",
    "state": "PUBLISHED"
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  "dataVersion": "5.2"
}