Threat Intelligence / CVE / CVE-2023-23397

CVE-2023-23397 — Microsoft Outlook

CISA KEV

CVSS v3.1 9.8 (CRITICAL) · EPSS 93.3% (higher than 99.8% of all scored CVEs) · Priority 9/10 · Published 2023-03-14

As of 2025-10-27, CVE-2023-23397 is a CRITICAL-severity vulnerability in Microsoft Outlook, CVSS v3.1 9.8, EPSS 93.3% (99.8th percentile). It is listed in the CISA Known Exploited Vulnerabilities catalog (added 2023-03-14), with a US federal remediation deadline of 2023-04-04. Threadlinqs Intelligence links 2 tracked threat campaigns to CVE-2023-23397, most recently “Russia (GRU Unit 26165 / APT28) Runs Multi-Vector Surveillance, Intimidation, Sabotage and Cyber Espionage Campaign Against Europe's Ukraine Defence Supply Chain”.

Last updated: 2025-10-27

What is CVE-2023-23397?

Microsoft Outlook Elevation of Privilege Vulnerability

The record classifies CVE-2023-23397 under weakness classes CWE-20, CWE-294. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 6 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 1279 days ago.

Severity and exploitation probability

CVSS v3.1 base score: 9.8 — CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS (FIRST): 93.3% probability of exploitation in the next 30 days, higher than 99.8% of all scored CVEs
CISA KEV: Listed since 2023-03-14, federal remediation deadline 2023-04-04
Threadlinqs priority: 9/10 — CISA KEV-listed, which Threadlinqs floors at 9
Published: 2023-03-14, last modified 2025-10-27

Is CVE-2023-23397 being exploited?

CISA added CVE-2023-23397 to the Known Exploited Vulnerabilities catalog on 2023-03-14, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2023-04-04 under BOD 22-01. It currently carries a trending score of 40 in the Threadlinqs vulnerability feed.

Affected products and versions

Microsoft: 365 Apps, Office 2019, Office Long Term Servicing Channel 2021, Outlook 2013, Outlook 2016

Showing 5 of 6 recorded product entries.

How to fix CVE-2023-23397

The record marks a vendor fix as available for CVE-2023-23397. Patch reference: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-23397. Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-23397. Because CVE-2023-23397 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2023-04-04. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

Threat activity tracking CVE-2023-23397

2 tracked threats in the Threadlinqs corpus reference CVE-2023-23397, either in the campaign’s CVE list or as an indicator on the campaign record.

Russia (GRU Unit 26165 / APT28) Runs Multi-Vector Surveillance, Intimidation, Sabotage and Cyber Espionage Campaign Against Europe's Ukraine Defence Supply Chain — HIGH · 2026-08-16
APT28/UAC-0001 Sustained Cyber Espionage Against Ukraine & EU (2024-2026 New TTPs) — HIGH · 2026-02-12

Sources

Seeded from nvd and not yet processed by the Threadlinqs enrichment pipeline, so blank CVSS, EPSS or KEV fields above mean NOT MEASURED rather than measured-absent.

Full detection coverage & IOCs for threats exploiting CVE-2023-23397 are available via the Threadlinqs MCP server (Purple tier). View plans →

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