CVE-2021-26855
CRITICALCVSS 9.1/10Actively ExploitedEPSS 100.00%
Last modified
CVE-2021-26855 is a critical-severity vulnerability rated 9.1/10 on the CVSS scale. Microsoft Exchange Server Remote Code Execution Vulnerability. CISA has confirmed active exploitation in the wild. EPSS estimates a 100.00% chance of exploitation in the next 30 days.
Description
Microsoft Exchange Server Remote Code Execution Vulnerability
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
100.0th percentile
Probability of exploitation in the next 30 days. Learn more
Exploitation Status
This vulnerability is listed in CISA’s Known Exploited Vulnerabilities catalog, confirming active exploitation in the wild. Federal agencies must remediate by .
Weakness Enumeration
Affected Software
| Vendor | Product | Versions | Update |
|---|---|---|---|
| Microsoft | Exchange Server | 2013 | Cumulative Update 21 |
| Microsoft | Exchange Server | 2016 | Cumulative Update 10 |
| Microsoft | Exchange Server | 2019 | — |
References
- http://packetstormsecurity.com/files/161846/Microsoft-Exchange-2019-SSRF-Arbitrary-File-Write.htmlExploit, Third Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.htmlExploit, Third Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/162610/Microsoft-Exchange-2019-Unauthenticated-Email-Download.htmlExploit, Third Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/162736/Microsoft-Exchange-ProxyLogon-Collector.htmlExploit, Third Party Advisory, VDB Entry
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26855Patch, Vendor Advisory
- http://packetstormsecurity.com/files/161846/Microsoft-Exchange-2019-SSRF-Arbitrary-File-Write.htmlExploit, Third Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.htmlExploit, Third Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/162610/Microsoft-Exchange-2019-Unauthenticated-Email-Download.htmlExploit, Third Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/162736/Microsoft-Exchange-ProxyLogon-Collector.htmlExploit, Third Party Advisory, VDB Entry
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26855Patch, Vendor Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26855US Government Resource
Timeline
- Published
- Last Modified
- Status
- Analyzed
Frequently Asked Questions
What is CVE-2021-26855?
Microsoft Exchange Server Remote Code Execution Vulnerability
How severe is CVE-2021-26855?
CVE-2021-26855 has a CVSS score of 9.1/10 (CRITICAL severity). The EPSS model estimates a 100.00% probability of exploitation in the next 30 days. This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog.
How do I fix CVE-2021-26855?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.
How Strix Helps
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- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
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- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
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Are you affected by CVE-2021-26855?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST