CVE-2021-31196
Microsoft Exchange Server Remote Code Execution Vulnerability
- CVSS
- 7.2Highscored by the publisher (CNA)
- Exploited in the wild
- Yes, in CISA KEV since 21 Aug 2024CISA deadline for US federal agencies: 11 Sept 2024
- EPSS
- 54.1%chance of exploitation in the next 30 daystop 1% of scored CVEsFIRST score of 11 Nov 2026
- Fix
- Patch availablesee the advisories in the references
- Published
- 14 Jul 2021analysed here 12 Nov 2026
Do first. Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable. (CISA's required action for this KEV entry)
Summary
Triage
- Exploitable
- At runtime
- Attack vector
- network
The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.
Affected products
| Product | Affected versions | Vendor says fixed in |
|---|---|---|
| Microsoft Microsoft Exchange Server 2013 Cumulative Update 23 | >= 15.00.0 and < 15.00.1497.023Vendor says fixed in: not stated | |
| Microsoft Microsoft Exchange Server 2016 Cumulative Update 20 | >= 15.01.0 and < 15.01.2242.012Vendor says fixed in: not stated | |
| Microsoft Microsoft Exchange Server 2016 Cumulative Update 21 | >= 15.01.0 and < 15.01.2308.014Vendor says fixed in: not stated | |
| Microsoft Microsoft Exchange Server 2019 Cumulative Update 10 | >= 15.02.0 and < 15.02.0922.013Vendor says fixed in: not stated | |
| Microsoft Microsoft Exchange Server 2019 Cumulative Update 9 | >= 15.02.0 and < 15.02.0858.015Vendor says fixed in: not stated |
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.
Products named in our analysis
- microsoft:exchange_server
Fix and mitigation
WAF and other mitigations
Can a WAF block it? Partly. The bug can be reached over the network, so generic WAF rules may stop some attacks. Its weakness type is unknown, so we cannot be more precise.
Also consider: patch
Based on the weakness type only; no CVE-specific evidence yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Remediation steps (AI-written)
Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.
Exploitation evidence
- CISA KEV catalog
- Listed since 21 Aug 2024.
- CISA due date
- 11 Sept 2024, the remediation deadline for US federal agencies
- CISA required action
- Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
- Public exploit code
- None on record in Exploit-DB, Metasploit, Nuclei templates or PoC-in-GitHub.
- CISA SSVC
- exploitation active, automatable yes, technical impact totalAssessed by CISA 28 Jan 2025 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.
Timeline
- 14 Jul 2021Published
- 21 Aug 2024Added to CISA KEV (exploited in the wild)1,133 days (about 3 years) later
- 11 Sept 2024CISA remediation due date (US federal agencies)21 days later
- 28 Jan 2025CISA SSVC assessment: exploitation active140 days (about 5 months) later
- 10 Aug 2026CVE record last updated559 days (about 2 years) later
- 12 Nov 2026Analysed by vulneraibility.com94 days (about 3 months) later
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
| Metric | Value | What it means |
|---|---|---|
| Attack vector | NetworkReachable over the internet or any routable network. | Reachable over the internet or any routable network. |
| Attack complexity | LowRepeatable attack, no special conditions. | Repeatable attack, no special conditions. |
| Privileges required | HighThe attacker needs admin-level privileges. | The attacker needs admin-level privileges. |
| User interaction | NoneNo victim action needed. | No victim action needed. |
| Scope | UnchangedImpact stays within the vulnerable component. | Impact stays within the vulnerable component. |
| Confidentiality | HighTotal data disclosure possible. | Total data disclosure possible. |
| Integrity | HighComplete modification possible. | Complete modification possible. |
| Availability | HighFull outage possible. | Full outage possible. |
Common questions
Is CVE-2021-31196 being exploited?
Yes. CVE-2021-31196 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2021-31196?
CVE-2021-31196 is rated High with a CVSS score of 7.2. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2021-31196?
Yes. A fix has been recorded for CVE-2021-31196. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2021-31196 affect?
CVE-2021-31196 affects microsoft:exchange_server. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
References
3 references in the CVE record, grouped by the tags the record gives them.
Patches (1)
- msrc.microsoft.com /update-guide/vulnerability/CVE-2021-31196
Other links (2)
- portal.msrc.microsoft.com /en-US/security-guidance/advisory/CVE-2021-31196
- cisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-31196
Where the data on this page comes from
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.
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