Security Digest · Vulnerability record · Known exploited
CVE-2021-31196: Microsoft Exchange Server Information Disclosure Vulnerability
Exploited in the wild (CISA KEV). Microsoft Exchange Server Remote Code Execution Vulnerability
CISA KEV · added 2024-08-21 CVSS 7.2 High EPSS 54.1% · p99
Should you act?
Exploited: patch now if you run it
CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Yes, if you run Microsoft Exchange Server. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2024-08-21, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2024-09-11; treat that as the outer limit, not the target.
- EPSS 54.1%, percentile 99: FIRST’s model estimates a 54.1% chance of exploitation activity in the next 30 days, higher than 99% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Needs an account (high (admin)). Exposure depends on who can log in.
What it is
Microsoft Exchange Server Remote Code Execution Vulnerability
CISA’s summary
Microsoft Exchange Server contains an information disclosure vulnerability that allows for remote code execution.
Product: Microsoft Exchange Server · Assigned by: microsoft · Published: 2021-07-14
Affected and fixed versions
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| Microsoft | Microsoft Exchange Server 2013 Cumulative Update 23 | 15.00.0 < 15.00.1497.023 |
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 20 | 15.01.0 < 15.01.2242.012 |
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 21 | 15.01.0 < 15.01.2308.014 |
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 10 | 15.02.0 < 15.02.0922.013 |
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 9 | 15.02.0 < 15.02.0858.015 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| microsoft | 3.1 | 7.2 High | CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: high (admin)
- User interaction: none
- Scope: unchanged
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: added 2024-08-21; federal due date 2024-09-11. Known ransomware use: Unknown.
- CISA required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
- CISA SSVC assessment: exploitation active, automatable yes, technical impact total.
- FIRST EPSS (model of 2026-10-21): 54.06% probability of exploitation activity in the next 30 days; percentile 99.
Timeline
- — CVE record published by microsoft
- — Added to CISA’s Known Exploited Vulnerabilities catalog
- — CISA remediation deadline for US federal agencies
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vendor and project advisories, patches
- Microsoft Exchange Server Remote Code Execution Vulnerability msrc.microsoft.com
- Listed in CISA KEV notes (msrc.microsoft.com) msrc.microsoft.com
Vulnerability records
- CVE.org record CVE-2021-31196 cve.org
- NVD entry CVE-2021-31196 nvd.nist.gov
Government
Other references from the CVE record and advisory
- portal.msrc.microsoft.com portal.msrc.microsoft.com
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