CVE-2021-31196
Microsoft Exchange Server · Email
Microsoft Exchange Server Information Disclosure Vulnerability
At a glance
Exploited. Added to CISA’s catalog of exploited vulnerabilities on August 21, 2024.
Affected product: Microsoft Exchange Server (category Email, indicative classification). Name in CISA’s catalog: Microsoft Exchange Server.
Microsoft component: Exchange Server (Messaging and collaboration).
What should I do?
Apply the patches or mitigations from Microsoft; if none are available, stop using the product.
Deadline set by CISA for US federal agencies: 21 days (due September 11, 2024). It only binds those agencies, but it is a useful measure of urgency.
- CVE-2021-31196 in Microsoft’s Security Update Guide
- Microsoft security advisories page (general page, not the advisory for this vulnerability)
- The vendor’s specific advisory is listed in the NVD references: CVE-2021-31196 on the NVD website.
Original text of the required action (CISA)
Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
Timeline
- Vulnerability published Publication date (NVD)
- Exploitation confirmed Added to CISA’s KEV catalog
- CISA deadline Remediation deadline set for US federal agencies
The facts, with their sources
- Exploitation confirmed
- Yes, on August 21, 2024 Date added to the catalog of exploited vulnerabilities. Exploitation itself may have started earlier. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- Ransomware
- No known use to date That does not guarantee it is not being used: the information is not public. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- Hunt for compromise
- Not requested by CISA Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- CISA required action
- Apply the patches or mitigations from Microsoft; if none are available, stop using the product. Rewritten by this site from CISA’s original text. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- CISA deadline
- September 11, 2024, 21 days Set for US federal agencies: a measure of urgency, not an obligation elsewhere. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- Microsoft patch
- Not available Source: Security Update Guide, collected September 29, 2026 at 14:57 UTC
- Vulnerability published
- July 14, 2021 Source: National Vulnerability Database (NVD), collected September 29, 2026 at 15:00 UTC
- Product according to CISA
- Microsoft Exchange Server Filed by this site under “Email” (indicative classification). Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H Technical detail of the score: attack vector, complexity, impact. Source: National Vulnerability Database (NVD), collected September 29, 2026 at 15:00 UTC
Severity and activity
FIRST’s EPSS model. Since exploitation is already confirmed, this figure is mostly useful to compare activity. Collected Sep 29, 2026.
Description
Microsoft Exchange Server Remote Code Execution Vulnerability
Official description from the NVD, collected Sep 29, 2026. CVE® description © The MITRE Corporation.
Microsoft Exchange Server contains an information disclosure vulnerability that allows for remote code execution.
Summary from CISA (KEV catalog).
CERT-FR advisories
No advisory among the latest CERT-FR publications this site follows. That does not mean there are none.
Information reused under the Open Licence 2.0 (Etalab); the date of last update is shown for each advisory. This site is neither affiliated with nor endorsed by ANSSI.
Sources for this page
- CISA KEV catalog: exploitation, date added, required action, deadline, ransomware.
- Microsoft Security Update Guide: product, patch.
- NVD (NIST): CVSS severity, publication date, description, vendor references.
- EPSS (FIRST): probability of exploitation.
- CERT-FR: advisories and alerts (in French).
- Brand and category: indicative classification by this site (method).