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CVE-2026-105242— Apache log4net: Request validation failure drops the event in the aspnet-request converter

Quick assessment

Affected
Apache Software Foundation Apache log4net
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Apache log4net 中 aspnet-request 模式转换器的异常条件处理不当漏洞 读取请求参数会触发 ASP.NET 请求验证，因此，携带包含标记（markup）等内容的请求会导致布局（layout）引发异常，进而导致附加器（appender）丢弃整个事件。攻击者（发送者）可以抑制自身请求的日志记录。仅使用 %aspnet-request 布局的 .NET Framework ASP.NET 应用程序会受到此问题影响。 此漏洞影响 Apache log4net：从 1.2.11 至 3.5.0 之前

CVSS 5.3 · Medium

Possible ATT&CK Techniques 1 AI

T1078.001 · Default Accounts

Affected Version Matrix 2

VendorProduct Version RangeStatus
Apache Software Foundation Apache log4net 1.2.11< 3.5.0 affected
243f1e9f3ee235955bade4b4fe664a903378719a< 145203420c579a703008b4b723b6a080757f4964 affected
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I. Basic Information for CVE-2026-105242

Vulnerability Information
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Vulnerability Title
Apache log4net: Request validation failure drops the event in the aspnet-request converter
Source: CVE Program / CVE List V5
Vulnerability Description
Improper Handling of Exceptional Conditions vulnerability in the aspnet-request pattern converter of Apache log4net. Reading request parameters triggers ASP.NET request validation, so a request carrying content such as markup made the layout throw and the appender discarded the whole event. A sender could suppress the log record of their own request. Only applications on ASP.NET for .NET Framework whose layout uses %aspnet-request are affected. This issue affects Apache log4net: from 1.2.11 before 3.5.0. Users are recommended to upgrade to version 3.5.0, which fixes the issue.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对异常条件的处理不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Apache Software Foundation Apache log4net 1.2.11 ~ 3.5.0 -
Apache Software Foundation Apache log4net 243f1e9f3ee235955bade4b4fe664a903378719a ~ 145203420c579a703008b4b723b6a080757f4964 -

II. Public POCs for CVE-2026-105242

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III. Intelligence Information for CVE-2026-105242

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Other References for CVE-2026-105242 (3)

Same Patch Batch · Apache Software Foundation · 2026-10-06 · 8 CVEs total

CVE-2026-94114 5.9 MEDIUM Apache Commons BCEL: Nested Code/Record attributes drive unbounded parse-time recursion in
CVE-2026-105244 5.3 MEDIUM Apache log4net: RemoteSyslogAppender silently deletes non-ASCII content
CVE-2026-105243 5.3 MEDIUM Apache log4net: Oversize EventLogAppender record silently discarded
CVE-2026-105241 5.3 MEDIUM Apache log4net: Unencodable content discards a whole SmtpPickupDirAppender batch
CVE-2026-105240 5.3 MEDIUM Apache log4net: NUL character truncates OutputDebugStringAppender records
CVE-2026-105239 5.3 MEDIUM Apache log4net: NUL character truncates EventLogAppender records
CVE-2026-105111 4.7 MEDIUM Apache Commons BCEL: Class2HTML emits unescaped class strings, enabling stored XSS

IV. Related Vulnerabilities

Same product: Apache log4net
Same vendor: Apache Software Foundation
Same weakness: CWE-755

V. Comments for CVE-2026-105242

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