""ET EXPLOIT Possible Microsoft Exchange RCE with Python PSRP Client UA Inbound (CVE-2021-34473)""

SID: 2033712

Revision: 1

Class Type: attempted-admin

Metadata: affected_product Microsoft_Exchange, attack_target Server, created_at 2021_08_12, cve CVE_2021_34473, deployment Perimeter, deployment Internal, signature_severity Major, tag Exploit, updated_at 2022_12_23, mitre_tactic_id TA0001, mitre_tactic_name Initial_Access, mitre_technique_id T1190, mitre_technique_name Exploit_Public_Facing_Application

Reference:

  • cve

  • 2021-34473

Protocol: tcp

Source Network: any

Source Port: any

Destination Network: [$HOME_NET,$HTTP_SERVERS]

Destination Port: [443,444]

Flow: established,to_server

Contents:

  • Value: "POST"

  • Value: "/autodiscover/autodiscover.json?"

  • Value: "Python|20|PSRP|20|Client"

Within:

PCRE: "/^User-Agent\x3a\x20[^\r\n]+Python\x20PSRP\x20Client/Hmi"

Special Options:

  • http_method

  • http_uri

  • fast_pattern

  • http_header

source