Microsoft Exchange Server Information Disclosure
CVE-2021-31196 is a high-severity vulnerability in Microsoft Exchange Server 2013 Cumulative Update 23 from Microsoft, with a CVSS 3.1 base score of 7.2 out of 10. It can be exploited remotely over the network by an attacker with administrator privileges, without any action from a user. The record lists version 15.00.1497.023 as the first without the flaw, so updating Microsoft Exchange Server 2013 Cumulative Update 23 to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on August 21, 2024, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Microsoft Exchange Server 2013 Cumulative Update 23 to 15.00.1497.023 or a later version.
- Update Microsoft Exchange Server 2016 Cumulative Update 20 to 15.01.2242.012 or a later version.
- Update Microsoft Exchange Server 2016 Cumulative Update 21 to 15.01.2308.014 or a later version.
- CISA's required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
- Read the advisory on msrc.microsoft.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Microsoft | Microsoft Exchange Server 2013 Cumulative Update 23 | 15.00.0 up to, but not including, 15.00.1497.023 | 15.00.1497.023 |
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 20 | 15.01.0 up to, but not including, 15.01.2242.012 | 15.01.2242.012 |
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 21 | 15.01.0 up to, but not including, 15.01.2308.014 | 15.01.2308.014 |
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 10 | 15.02.0 up to, but not including, 15.02.0922.013 | 15.02.0922.013 |
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 9 | 15.02.0 up to, but not including, 15.02.0858.015 | 15.02.0858.015 |
| Microsoft | Exchange Server | 2013; 2016; 2019 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- HighAdministrator-level access is required first.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.2 | High | CNA (microsoft.com) |
| CVSS 3.1 | 7.2 | High | NVD |
| CVSS 2.0 | 6.5 | Medium | NVD |
Official description
Microsoft Exchange Server Remote Code Execution Vulnerability
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-31196US Government Resource
Other vulnerabilities in Microsoft Exchange Server 2013 Cumulative Update 23
- 8.8 High severity
- 9.8 Critical severity
- 8.0 High severity
- 8.8 High severity
- 9.8 Critical severity
- 9.8 Critical severity
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