6.3

CVSS Score

4.0

-

CVSS Score

Basic Information

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CVE-2026-24819

CVE-2026-24819: weixin4j has Improperly Controlled Sequential Memory Allocation

Improperly Controlled Sequential Memory Allocation vulnerability in foxinmy weixin4j (weixin4j-base/src/main/java/com/foxinmy/weixin4j/util modules). This vulnerability is associated with program files CharArrayBuffer.Java, ClassUtil.Java.

This issue affects all versions of weixin4j. A path is available: d1c8258

(GitHub Advisory)

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CVE-2026-24819

CVE-2026-24819:

6.3

CVSS Score

4.0

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
com.foxinmy:weixin4j-base	maven	<= 1.10.2

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The analysis of the provided patches reveals two modified functions. The primary vulnerability, 'Improperly Controlled Sequential Memory Allocation' (CWE-1325), is located in the ensureCapacity method of the com.foxinmy.weixin4j.util.CharArrayBuffer class. The vulnerability stems from an integer overflow that can occur when calculating the required buffer size. An attacker could potentially exploit this by providing input that causes the capacity calculation (this.len + required) to exceed Integer.MAX_VALUE, wrapping the value around to a small number. This leads to the allocation of a buffer that is too small, and subsequent data writes can overflow this buffer, resulting in a heap overflow. The patch mitigates this by using long for the capacity calculation to prevent the overflow and adds a check against a maximum capacity.

The second modified function, getDefaultClassLoader in com.zone.weixin4j.util.ClassUtil, was also included in the patch. However, the changes here address a different concern related to exception handling when accessing the ClassLoader in an environment with a SecurityManager. While this is a valid security improvement, it does not align with the described memory allocation vulnerability. It is included in this analysis because it was part of the provided commit history and mentioned in the vulnerability description, but it is considered a secondary finding with low confidence in relation to the core CVE.

Vulnerable functions

com.foxinmy.weixin4j.util.CharArrayBuffer.ensureCapacity

weixin4j-base/src/main/java/com/foxinmy/weixin4j/util/CharArrayBuffer.java

The `ensureCapacity` function is vulnerable to an integer overflow. The calculation `this.len + required` can wrap around if the sum exceeds the maximum integer value. This would result in `expand()` being called with a much smaller value than expected, leading to the allocation of an undersized buffer. Subsequent writes to this buffer can cause a heap-based buffer overflow.

com.zone.weixin4j.util.ClassUtil.getDefaultClassLoader

weixin4j-serverX/src/main/java/com/zone/weixin4j/util/ClassUtil.java

Although mentioned in the vulnerability description, the change in this function addresses a different type of issue. The original code used a broad `catch (Throwable ex)` which could hide `SecurityException` when running under a Java Security Manager. The patch adds explicit handling for `SecurityException`. This is a security hardening measure but does not directly relate to the 'Improperly Controlled Sequential Memory Allocation' vulnerability.

Vulnerability Intelligence
Miggo AI

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WAF Protection Rules

WAF Rule

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Reasoning

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