cbcvebase.
CVE-2023-23397
published 2023-03-14

CVE-2023-23397: Microsoft Outlook Elevation of Privilege Vulnerability

PriorityP197critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
KEVITWEXPLOITRansomwareInitial access
CISA Known Exploited Vulnerabilitydue 2023-04-04
Exploited in the wild
EPSS
97.41%
99.9th percentile
Microsoft Outlook Elevation of Privilege Vulnerability

Affected

36 ranges· showing 25
VendorProductVersion rangeFixed in
microsoftmicrosoft_365_apps_for_enterprise>= 16.0.1 < https://aka.ms/OfficeSecurityReleaseshttps://aka.ms/OfficeSecurityReleases
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
microsoftmicrosoft_outlook_2013_service_pack_1>= 15.0.0.0 < 15.0.5537.100015.0.5537.1000
microsoftmicrosoft_outlook_2016>= 16.0.0.0 < 16.0.5387.100016.0.5387.1000
microsoftoffice
microsoftoffice_long_term_servicing_channel
microsoftoutlook
microsoftoutlook
msrcmicrosoft_365_apps_for_enterprise_for_32-bit_systems
msrcmicrosoft_365_apps_for_enterprise_for_64-bit_systems
msrcmicrosoft_exchange_server_2016_cumulative_update_23
msrcmicrosoft_exchange_server_2019_cumulative_update_13
msrcmicrosoft_exchange_server_2019_cumulative_update_14
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
msrcmicrosoft_outlook_2013_rt_service_pack_1
msrcmicrosoft_outlook_2013_service_pack_1
msrcmicrosoft_outlook_2016
msrcwindows_10
msrcwindows_10_version_1607
msrcwindows_10_version_1809
msrcwindows_10_version_20h2

Detection & IOCsextracted from sources · hover to see the quote

ip5.199.162.132
ip101.255.119.42
ip181.209.99.204
ip213.32.252.221
ip168.205.200.55
ip69.162.253.21
ip185.132.17.160
ip69.51.2.106
ip113.160.234.229
ip85.195.206.7
hash52951f2d92e3d547bad86e33c1b0a8622ac391c614efa3c5d167d8a825937179
hash4f3992b9dbd1c2a64588a5bc23f1b37a12a4355688d6e1a06408ea2449c59368
port445
port56981
port8080
urlhttps://tinyurl.com/app/api/create
domainmockbin.org
domainfree.keep.sh
path%APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup\search.url
cookieXSRF-TOKEN
  • Block outbound TCP/445 (SMB) at the network perimeter to prevent Net-NTLMv2 hash exfiltration triggered by CVE-2023-23397 exploit emails.
  • The exploit is triggered when Outlook processes a specially crafted email containing a UNC path in an extended MAPI property pointing to an attacker-controlled SMB share — no user interaction or Preview Pane opening is required.
  • The NTLM hash leak fires when the Outlook reminder window is displayed; an already-expired reminder fires immediately upon receipt, so detection should also cover immediate outbound SMB connections upon email arrival.
  • Pawn Storm used compromised EdgeOS routers as SMB callback servers (port 445) for CVE-2023-23397 exploits, combined with SOCKS5 proxies on port 56981 and Werkzeug/Waitress implants on port 8080 — hunt for outbound SMB to EdgeOS router IPs.
  • A PowerShell-based Net-NTLMv2 hash stealer (SHA256: 52951f2d92e3d547bad86e33c1b0a8622ac391c614efa3c5d167d8a825937179) spawns two background processes sending requests to localhost:8080 to trigger NTLMv2 authentication via WebDAV and then exfiltrates the AUTHENTICATE message to mockbin.org.
  • The patch (CVE-2023-23397 fix) can be bypassed via CVE-2023-29324 by forging the malicious UNC path in a particular format; ensure the May 2023 patch is also applied and monitor Exchange-side stripping of extended MAPI properties.
  • Malicious samples arrive as MSG, EML, or TNEF-format attachments; hunt for TNEF attachments containing calendar/task objects with UNC paths in extended MAPI properties pointing to external IPs.
  • ·The vulnerability only leaks Net-NTLMv2 hashes via SMB (port 445); WebDAV fallback does NOT leak credentials to external entities because Windows honors internet security zone checks for WebDAV.
  • ·Microsoft-hosted online services (e.g., Microsoft 365 / Outlook on the web) are NOT affected; only self-hosted/on-premises Outlook for Windows (2013 through current) is vulnerable.
  • ·The leaked Net-NTLMv2 hash belongs to the Windows user currently signed in to the device running Outlook, NOT necessarily the identity that received the malicious message.
  • ·Net-NTLMv2 hashes obtained via this exploit CANNOT be used in Pass-the-Hash attacks; they can only be used for NTLM relay attacks or offline dictionary/brute-force cracking.
  • ·Even on a patched Outlook client, UNC paths pointing to intranet/trusted zones can still trigger SMB or WebDAV credential leaks locally; the Exchange-side hotfix (stripping extended MAPI properties) is the more reliable mitigation.

CVSS provenance

nvdv3.19.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vulncheck9.8CRITICAL
cisa9.8CRITICAL
vendor_msrc9.8CRITICAL
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