Pulse Connect Secure Authentication Bypass and Remote Code Execution Vulnerability Advisory (CVE-2021-22893)
Executive & SecOps Summary
SECOPS ASSESSMENTPulse Connect Secure 9.0R3/9.1R1 and higher
Unauthenticated remote attackers can bypass authentication and execute arbitrary code with root privileges via Windows File Share Browser and Collaboration features
Apply official vendor patches immediately, or import the mitigation XML workaround to disable vulnerable features
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Upgrade to the latest secure release (9.1R11.4 or higher) immediately. For clustered environments, apply the update sequentially to all active and passive nodes.
2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, import the following workaround XML configuration via the PCS Admin Console (Maintenance -> Import/Export -> Import XML) to disable the vulnerable features.
# Import this XML structure to block access to the vulnerable endpoints
# Affected features: Windows File Share Browser, Pulse Secure Collaboration
<configuration>
<system>
<filters>
<filter-rule>
<name>Block-CVE-2021-22893</name>
<url-pattern>^/dana/fb/smb/.*|^/dana-cached/fb/smb/.*|^/dana/collab/.*</url-pattern>
<action>deny</action>
</filter-rule>
</filters>
</system>
</configuration>3. Log Audit & IoC Verification Commands
Run the Pulse Secure Integrity Checker Tool to verify system file integrity, and inspect web access logs for suspicious requests targeting the vulnerable endpoints.
# Scan web access logs for unauthorized attempts to access SMB or Collaboration features
grep -E '/dana/fb/smb/|/dana-cached/fb/smb/|/dana/collab/' /var/log/pulsesecure/web_access.log
# Check the output of the system integrity tool for any modified or mismatched files
cat /home/perl/integrity_check_results.txt | grep -i 'mismatch'Stop Exposing VPN Ports to the Internet — Switch to Zero-Trust Access
Eliminate public-facing VPN concentrators and firewall management ports with identity-first Zero-Trust Network Access.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2021-22893) is a critical authentication bypass (CWE-287) combined with a Use-After-Free (CWE-416) flaw in Pulse Connect Secure (PCS). It resides within the Windows File Share Browser and Pulse Secure Collaboration components. The root cause is improper input validation and memory management when handling specific URI requests, allowing unauthenticated users to manipulate memory states.
2. Exploitation Mechanics & Attack Scenario
An attacker sends crafted HTTP requests to the exposed PCS gateway interface. These requests bypass the authentication layer and target the vulnerable file share browser or collaboration endpoints. This triggers a Use-After-Free condition, allowing the attacker to hijack the execution flow and execute arbitrary commands with root privileges on the underlying gateway operating system.
3. Infrastructure & Business Impact
With a CVSS score of 10.0, this vulnerability has been actively exploited in the wild by advanced persistent threat (APT) actors. Successful exploitation grants full administrative control over the VPN gateway, enabling attackers to intercept enterprise traffic, harvest Active Directory credentials, and perform lateral movement across the internal network.
Official Vendor Advisories & References
Pulse Connect Secure 9.0R3/9.1R1 and higher is vulnerable to an authentication bypass vulnerability exposed by the Windows File Share Browser and Pulse Secure Collaboration features of Pulse Connect Secure that can allow an unauthenticated user to perform remote arbitrary code execution on the Pulse Connect Secure gateway. This vulnerability has been exploited in the wild.
Frequently Asked SecOps Questions (CVE-2021-22893)
FAQQ1. How critical is CVE-2021-22893 and is it actively exploited in the wild?
CVE-2021-22893 is rated CVSS 10.0 (CRITICAL) with a 30-day EPSS exploitation probability of 47.5%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2021-22893?
Primary impacted vendors include pulsesecure across pulse_connect_secure. Scope summary: Pulse Connect Secure 9.0R3/9.1R1 and higher (all 9.X versions prior to patched releases)
Q3. What temporary mitigations or workarounds exist for CVE-2021-22893 before patching?
[Mitigation] Apply official vendor patches immediately, or import the mitigation XML workaround to disable vulnerable features Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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