cbcvebase.
CVE-2024-38200
published 2024-08-08

CVE-2024-38200: Microsoft Office Spoofing Vulnerability Microsoft Office Spoofing Vulnerability

critical9.1CVSS 3.1
AVNACLPRNUINSUCHIHAN
EXPLOIT
EPSS
20.30%
97.2th percentile
Microsoft Office Spoofing Vulnerability Microsoft Office Spoofing Vulnerability

Affected

11 ranges
VendorProductVersion rangeFixed in
microsoftmicrosoft_365_apps_for_enterprise>= 16.0.1 < https://aka.ms/OfficeSecurityReleaseshttps://aka.ms/OfficeSecurityReleases
microsoftmicrosoft_office_2016>= 16.0.0 < 16.0.5461.100116.0.5461.1001
microsoftmicrosoft_office_2019>= 19.0.0 < https://aka.ms/OfficeSecurityReleaseshttps://aka.ms/OfficeSecurityReleases
microsoftmicrosoft_office_ltsc_2021>= 16.0.1 < https://aka.ms/OfficeSecurityReleaseshttps://aka.ms/OfficeSecurityReleases
msrcmicrosoft_365_apps_for_enterprise_for_32-bit_systems
msrcmicrosoft_365_apps_for_enterprise_for_64-bit_systems
msrcmicrosoft_office_2016
msrcmicrosoft_office_2019_for_32-bit_editions
msrcmicrosoft_office_2019_for_64-bit_editions
msrcmicrosoft_office_ltsc_2021_for_32-bit_editions
msrcmicrosoft_office_ltsc_2021_for_64-bit_editions

Detection & IOCsextracted from sources · hover to see the quote

otherms-word:ofe|u|http://hostname:port/leak.docx
snort
alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET EXPLOIT Microsoft Office Spoofing to HTTP Redirect Inbound (CVE-2024-38200)"; flow:established,to_client; http.content_type; pcre:"/^(?:application\x2fjavascript|text\x2fhtml)$/"; http.response_body; content:"|7c|u|7c|http"; fast_pattern; pcre:"/ms-(?:word|powerpoint|excel|visio|access|project|publisher|spd|infopath)\x3a(?:of(?:e|v)|nft)\x7cu\x7chttps?\x3a\x2f{2}/i"; content:!"|2e|office|2e|net|2f|"; reference:url,github.com/passtheticket/CVE-2024-38200; reference:cve,2024-38200; classtype:bad-unknown; sid:2056375; rev:1; metadata:affected_product MS_Office, attack_target Client_Endpoint, tls_state TLSDecrypt, created_at 2024_10_01, cve CVE_2024_38200, deployment Perimeter, deployment SSLDecrypt, confidence High, signature_severity Major, tag Exploit, updated_at 2024_10_01; target:dest_ip;)
  • Detect inbound HTTP responses containing MS Office URI scheme redirects (ms-word, ms-excel, ms-powerpoint, etc.) with the ofe|u| or nft|u| pattern pointing to non-office.net URLs — the Snort/ET rule (sid:2056375) matches on content '|7c|u|7c|http' combined with the URI scheme PCRE and absence of '.office.net/'.
  • Monitor for outbound NTLM authentication (SMB/HTTP) triggered by Office URI scheme invocations (ms-word:, ms-excel:, etc.) to non-Microsoft hosts, which indicates forced NTLMv2 hash capture.
  • Alert on outbound TCP 445 (SMB) connections from workstations to external/untrusted IPs, which may indicate NTLM hash leakage triggered by a malicious Office URI.
  • Audit or block outgoing NTLM traffic to remote servers using the 'Network Security: Restrict NTLM: Outgoing NTLM traffic to remote servers' group policy; unexpected NTLM attempts to external hosts may indicate exploitation.
  • Watch for DNS A record creation by standard domain users (e.g., via dnstool.py) pointing to attacker-controlled IPs, which is a prerequisite step in the exploit chain to trigger automatic NTLMv2 authentication via Intranet Zone trust.
  • Monitor ntlmrelayx activity relaying captured NTLMv2 hashes to LDAP on domain controllers (port 389), which is the post-capture escalation step in the CVE-2024-38200 exploit chain.
  • ·The ET Snort rule (sid:2056375) requires TLS decryption to be effective against HTTPS-delivered payloads, as indicated by the 'tls_state TLSDecrypt' and 'deployment SSLDecrypt' metadata tags.
  • ·Blocking outbound NTLM traffic or TCP 445 may break legitimate access to remote servers and applications that rely on NTLM authentication — validate impact before enforcing.
  • ·Adding users to the Protected Users Security Group prevents NTLM use but may impact applications requiring NTLM; settings revert once the user is removed from the group.
  • ·A Feature Flighting fix was deployed on 7/30/2024 protecting in-support Office/M365 versions, but the final patch requires the August 13, 2024 update to be fully remediated.

CVSS provenance

nvdv3.19.1CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
cvelistv56.5MEDIUM
vendor_msrc6.5MEDIUM
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