【安全通报】微软Exchange多个高危漏洞（CVE-2021-26855等）

花屋敷 1355天前

Exchange 是微软公司的一套电子邮件服务组件，是个消息与协作系统。

近日，微软发布了Exchange 多个高危漏洞的风险通告，该漏洞编号为CVE-2021-26855，CVE-2021-26857，CVE-2021-26858，CVE-2021-27065。

CVE-2021-26855: 服务端请求伪造漏洞

Exchange服务器端请求伪造（SSRF）漏洞，利用此漏洞的攻击者能够发送任意HTTP请求并通过Exchange Server进行身份验证。

CVE-2021-26857: 反序列化漏洞

Exchange存在反序列化漏洞，该漏洞需要管理员权限，利用此漏洞的攻击者可以在Exchange服务器上以SYSTEM身份运行代码。

CVE-2021-26858/CVE-2021-27065: 任意文件写入漏洞

Exchange中身份验证后的任意文件写入漏洞。攻击者通过Exchange服务器进行身份验证后，可以利用此漏洞将文件写入服务器上的任何路径。该漏洞可以配合CVE-2021-26855 SSRF漏洞进行组合攻击。

CVE 编号

CVE-2021-26855
CVE-2021-26857
CVE-2021-26858
CVE-2021-27065

fofa查询语句

microsoft exchange 2013： 
app="Microsoft-Exchange-2013"||app="Microsoft-Exchange-Server-2013-CU21"||app="Microsoft-Exchange-Server-2013-CU17"||app="Microsoft-Exchange-Server-2013-CU23"||app="Microsoft-Exchange-Server-2013-CU13"||app="Microsoft-Exchange-Server-2013-CU22"||app="Microsoft-Exchange-Server-2013-CU11"||app="Microsoft-Exchange-Server-2013-CU2"||app="Microsoft-Exchange-Server-2013-CU16"||app="Microsoft-Exchange-Server-2013-CU19"||app="Microsoft-Exchange-Server-2013-CU3"||app="Microsoft-Exchange-Server-2013-CU18"||app="Microsoft-Exchange-Server-2013-CU5"||app="Microsoft-Exchange-Server-2013-CU20"||app="Microsoft-Exchange-Server-2013-CU12"||app="Microsoft-Exchange-Server-2013-CU15"||app="Microsoft-Exchange-Server-2013-CU10"||app="Microsoft-Exchange-Server-2013-CU9"||app="Microsoft-Exchange-Server-2013-CU6"||app="Microsoft-Exchange-Server-2013-CU7"||app="Microsoft-Exchange-Server-2013-CU1"||app="Microsoft-Exchange-Server-2013-CU14"||app="Microsoft-Exchange-Server-2013-CU8"||app="Microsoft-Exchange-Server-2013-RTM"||app="Microsoft-Exchange-Server-2013-SP1"||app="Microsoft-Exchange-2013"

microsoft exchange 2016： 
app="Microsoft-Exchange-Server-2016-CU19"||app="Microsoft-Exchange-Server-2016-CU3"||app="Microsoft-Exchange-Server-2016-CU12"||app="Microsoft-Exchange-Server-2016-RTM"||app="Microsoft-Exchange-Server-2016-CU7"||app="Microsoft-Exchange-Server-2016-CU17"||app="Microsoft-Exchange-Server-2016-CU2"||app="Microsoft-Exchange-Server-2016-CU1"||app="Microsoft-Exchange-Server-2016-CU14"||app="Microsoft-Exchange-Server-2016-CU5"||app="Microsoft-Exchange-Server-2016-CU11"||app="Microsoft-Exchange-Server-2016-CU9"||app="Microsoft-Exchange-Server-2016-CU16"||app="Microsoft-Exchange-Server-2016-CU10"||app="Microsoft-Exchange-Server-2016-CU6"||app="Microsoft-Exchange-Server-2016-CU13"||app="Microsoft-Exchange-Server-2016-CU18"||app="Microsoft-Exchange-Server-2016-CU8"||app="Microsoft-Exchange-Server-2016-CU4"||app="Microsoft-Exchange-2016-POP3-server"

microsoft exchange 2019：
app="Microsoft-Exchange-Server-2019-CU5"||app="Microsoft-Exchange-Server-2019-CU3"||app="Microsoft-Exchange-Server-2019-Preview"||app="Microsoft-Exchange-Server-2019-CU8"||app="Microsoft-Exchange-Server-2019-CU1"||app="Microsoft-Exchange-Server-2019-CU7"||app="Microsoft-Exchange-Server-2019-CU2"||app="Microsoft-Exchange-Server-2019-CU6"||app="Microsoft-Exchange-Server-2019-RTM"||app="Microsoft-Exchange-Server-2019-CU4"


microsoft exchange 2010： 
app="Microsoft-Exchange-2010-POP3-server-version-03.1"||app="Microsoft-Exchange-Server-2010"

影响范围

microsoft:exchange: 2013/2016/2019/2010

根据目前FOFA系统最新数据（一年内数据），显示全球范围内（app="Microsoft-Exchange"）共有 1,563,491 个相关服务对外开放。美国使用数量最多，共有 353,403 个；德国第二，共有 231,069 个；英国第三，共有 85,074 个；中国香港第四，共有 76,719 个；荷兰第五，共有 59,420 个。

全球范围内分布情况如下（仅为分布情况，非漏洞影响情况）

中国大陆地区上海使用数量最多，共有 8,557 个；广东第二，共有 6,846 个；北京第三，共有 5,060 个；江苏第四，共有 4,180 个；浙江第五，共有 1,803 个。

修复建议

微软已发布相关安全更新，用户可更新到安全版本。
CVE-2021-26855下载链接：
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26855
CVE-2021-26857下载链接：
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26855
CVE-2021-26858下载链接：
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26855
CVE-2021-27065下载链接：
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26855
临时修补建议：
CVE-2021-26855：服务端请求伪造漏洞
可以通过以下Exchange HttpProxy日志进行检测：
%PROGRAMFILES%\Microsoft\Exchange Server\V15\Logging\HttpProxy
通过以下Powershell可直接进行日志检测，并检查是否受到攻击：
```
Import-Csv -Path (Get-ChildItem -Recurse -Path “$env:PROGRAMFILES\Microsoft\Exchange Server\V15\Logging\HttpProxy” -Filter ‘*.log’).FullName | Where-Object {  $_.AuthenticatedUser -eq ” -and $_.AnchorMailbox -like ‘ServerInfo~*/*’ } | select DateTime, AnchorMailbox
```
如果检测到了入侵，可以通过以下目录获取攻击者采取了哪些活动
%PROGRAMFILES%\Microsoft\Exchange Server\V15\Logging
CVE-2021-26857：反序列化漏洞
该漏洞单独利用难度稍高，可利用以下命令检测日志条目，并检查是否受到攻击。
```
Get-EventLog -LogName Application -Source “MSExchange Unified Messaging” -EntryType Error | Where-Object { $_.Message -like “*System.InvalidCastException*” }
```
CVE-2021-26858：远程执行代码漏洞
日志目录：C:\ProgramFiles\Microsoft\ExchangeServer\V15\Logging\OABGeneratorLog
可通过以下命令进行快速浏览，并检查是否受到攻击：
```
findstr /snip /c:”Download failed and temporary file” “%PROGRAMFILES%\Microsoft\Exchange Server\V15\Logging\OABGeneratorLog\*.log”
```
CVE-2021-27065：任意文件写入漏洞
通过以下powershell命令进行日志检测，并检查是否遭到攻击：
```
Select-String -Path “$env:PROGRAMFILES\Microsoft\Exchange Server\V15
```