CVE-2021-22894 is a collaboration suite buffer overflow vulnerability in Ivanti Pulse Connect Secure. CISA added it to the Known Exploited Vulnerabilities catalogue on 3 November 2021, which means attackers have used it in real attacks. Organisations running the affected product should apply the vendor fix or mitigation as a priority.
What this vulnerability means in practice
A collaboration suite buffer overflow is dangerous because malformed input can overwrite memory in a security gateway or remote-access appliance. In products that sit in front of sensitive internal services, that kind of bug can become a direct entry point for remote code execution, session theft, or device compromise.
For this exact CVE, the important takeaway is not just that the flaw exists, but that it was added to CISA’s Known Exploited Vulnerabilities catalogue, which means it has been used in real attacks. That elevates it from a theoretical software defect to an active exposure that should be treated as urgent.
Why exploited edge-device flaws are high impact
When a buffer overflow lands in an internet-facing access product, the attacker is often operating at the trust boundary. That can let them reach authenticated users, internal applications, or administrative interfaces from a foothold that defenders assume is hardened. Exploited edge-device vulnerabilities also tend to be attractive because they can bypass normal perimeter assumptions and provide persistence on a system that is designed to broker trust.
For a practical example of how quickly exposed remote-access products can become credential and session targets, see Ivanti Connect Secure exploitation 2024. More broadly, remote-access infrastructure is a recurring target because it concentrates privileged entry paths, as covered in Remote Access Identity Guide.
How organisations should assess exposure
Exposure checks start with a precise asset inventory. Organisations need to know whether the affected product is deployed anywhere, whether it is internet-facing, and whether any instances are still reachable through NAT, published portals, or vendor-managed access paths. Vendor advisories and the CISA KEV catalogue should be the primary sources for version and remediation details, rather than secondary summaries.
Prioritisation should be based on actual deployment and reachability, not just on whether scanning tools happen to report a generic version string. For vulnerability triage and remediation discipline, the Vulnerability Management Guide is the most relevant internal reference in the supplied pool.
Remediation, detection, and compromise review
The preferred response is to apply the vendor fix or mitigation as soon as possible. If patching must wait, organisations should reduce exposure by restricting access, limiting administrative reach, and tightening monitoring around the device and its adjacent authentication paths. Because this kind of issue has been exploited in the wild, compensating controls are a stopgap, not a substitute for remediation.
After patching, teams should still review for signs of prior compromise. That includes unusual logins, unexpected configuration changes, new accounts or sessions, altered certificates or keys, and any evidence that the device was used as a launch point into internal systems. If compromise is suspected, treat the appliance as a trust-break event and investigate downstream systems as well as the vulnerable device itself.
Risk and Threat Considerations
Exploited buffer overflows in remote-access or collaboration appliances can expose the organisation to unauthorised access, device takeover, and lateral movement from a privileged perimeter position. The main risk is that the vulnerable system may already have been used as an initial foothold before defenders notice.
Failure mechanism: An attacker supplies malformed input that overflows memory, then uses the resulting code execution or crash behaviour to gain control of the appliance or disrupt its trust functions.
Impact: The compromise can lead to internal access, credential or session abuse, persistence on the edge device, and follow-on intrusion into connected systems.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
CIS Controls v8, NIST SP 800-53 Rev 5 and OWASP ASVS set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| CIS Controls v8 | CIS-7 — Continuous Vulnerability Management | This CVE requires prioritising exploited vulnerability remediation and verification. |
| Recommendation — Prioritise, track, and verify remediation for the affected appliance as an exploited vulnerability. | ||
| NIST SP 800-53 Rev 5 | RA-5 — Vulnerability Monitoring and Scanning | The issue is an actively exploited software weakness that must be discovered and tracked. |
| SI-2 — Flaw Remediation | The core response is to apply the vendor fix or mitigation for the identified flaw. | |
| SC-7 — Boundary Protection | The product sits at a trust boundary, so network exposure materially affects exploitability. | |
| Recommendation — Continuously scan for the affected product and validate exposure against current vulnerability intelligence. Remediate the flaw promptly and confirm the vulnerable instance is no longer reachable or exploitable. Restrict external access to the appliance and reduce the attack surface at the boundary. | ||
| OWASP ASVS | V15 — Secure Coding and Architecture | Buffer overflows are a software memory-safety weakness addressed by secure architecture and coding controls. |
| Recommendation — Use memory-safe design and secure coding review to prevent buffer overflow conditions in externally exposed components. | ||
Practitioner Guidance
Why practitioners should care: Treat KEV-listed edge-device flaws as operationally urgent because they are already proven in attack activity, and the exposed system often sits on a high-value trust boundary. Remediation priority should be driven by internet exposure and business criticality, not by maintenance convenience.
Practitioner takeaway: If the product is deployed anywhere in your environment, assume exposure until you can confirm inventory, reachability, patch status, and post-patch integrity.
Related resources from NHI Mgmt Group
- CVE-2025-22457 (Ivanti Connect Secure, Policy Secure, and ZTA Gateways Stack-Based Buffer Overflow)
- CVE-2025-0282 (Ivanti Connect Secure, Policy Secure, and ZTA Gateways Stack-Based Buffer Overflow)
- CVE-2021-22893 (Ivanti Pulse Connect Secure Use-After-Free)
- What are the signs that an Ivanti Connect Secure appliance may have been compromised by CVE-2025-22457?
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Reviewed and updated by the NHIMG editorial team on October 17, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org