Threats / Microsoft / CVE-2023-23397
CVE-2023-23397
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-08-04
Microsoft Office vulnerability
Microsoft Office Outlook privilege escalation vulnerability enabling NTLM Relay attacks to impersonate users against other services.
Verdict
Today item — known-exploited.
A privilege escalation flaw in Outlook allows attackers to intercept and relay NTLM authentication tokens, gaining unauthorized access to user accounts and connected services without requiring additional credentials.
CISA KEV Yes · 2023-03-145EPSS 0.97408 (verify live)6Exploit Weaponized · public PoC7CVSS 9.83CISA SSVC Exploitation: active · Automatable: no · Impact: total4
01
Is it exploitable?
— the evidence, ranked above the scoreExploit available
Fully weaponized — public exploit code is cataloged for this vulnerability.We link the existence of the exploit; we do not host or redistribute payloads.
Reported exploitation
63 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2023-03-14).
Probability (EPSS)
EPSS 0.97408 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 9.8 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C) · Affected: Microsoft, Office. Confirm exact fixed builds in the vendor advisory.CVSS — CNA-assigned (CVE.org), version 3.1, set at disclosure.
Weakness (CWE)
Mapped to CWE-20 Improper Input Validation.CWE — CNA-assigned (CVE.org); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: totalCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog the same day the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious message or calendar invite that triggers Outlook to initiate an NTLM authentication request to an attacker-controlled server.
Business
Users receive seemingly legitimate communications that silently compromise their authentication credentials.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I intercept the NTLM authentication token sent by Outlook and relay it to a legitimate internal service to authenticate as the victim user.
Business
Attackers gain unauthorized access to enterprise systems and data using stolen user credentials without triggering password-based detection.
3
Lateral reach — past segmentation narrative 3
Attacker
I access sensitive resources, modify configurations, or move laterally through the network using the compromised user's privileges.
Business
Confidential data is exposed, systems are compromised, and the attack may spread to critical infrastructure or connected organizations.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05