CVE-2021-22934 in Pulse Connect Secure
Summary
by MITRE • 08/16/2021
A vulnerability in Pulse Connect Secure before 9.1R12 could allow an authenticated administrator or compromised Pulse Connect Secure device in a load-balanced configuration to perform a buffer overflow via a malicious crafted web request.
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Analysis
by VulDB Data Team • 10/17/2022
The vulnerability identified as CVE-2021-22934 represents a critical buffer overflow flaw within Pulse Connect Secure appliances that affects versions prior to 9.1R12. This issue stems from inadequate input validation mechanisms within the web interface processing logic, specifically when handling crafted HTTP requests in load-balanced deployments. The vulnerability manifests when an authenticated administrator or an attacker who has compromised a device within a load-balanced configuration attempts to submit maliciously constructed web requests that exceed the allocated buffer space. Such buffer overflow conditions can lead to arbitrary code execution and complete system compromise.
The technical implementation of this vulnerability resides in the application layer of the Pulse Connect Secure platform where HTTP request parsing occurs. When the system processes incoming requests, it fails to properly validate the length and content of input parameters, particularly within the web interface components that manage administrative functions. The buffer overflow occurs during the parsing of user-supplied data in memory structures that are insufficiently sized to accommodate maliciously crafted inputs. This flaw aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which addresses heap-based buffer overflow scenarios. The vulnerability is particularly concerning because it requires only authentication privileges or compromise of a single device within a load-balanced cluster, making it exploitable in environments where security boundaries may be compromised.
The operational impact of CVE-2021-22934 extends beyond simple system instability, as it enables attackers to achieve complete administrative control over affected appliances. In load-balanced configurations, this vulnerability becomes even more dangerous because an attacker who compromises one device can potentially leverage it to attack other members of the cluster. The exploitation process typically involves crafting specific HTTP requests that trigger the buffer overflow condition, potentially leading to remote code execution with the privileges of the affected service. This capability allows attackers to establish persistent backdoors, exfiltrate sensitive data, or use the compromised appliances as launch points for further attacks within the network. The vulnerability also poses significant risk to organizations using Pulse Connect Secure for remote access and VPN services, as it could enable unauthorized access to corporate networks.
Organizations should implement immediate mitigation strategies including deployment of the vendor-provided security patches for Pulse Connect Secure versions 9.1R12 and later, which address the buffer overflow conditions through proper input validation and memory management controls. Network segmentation and access controls should be enhanced to limit the exposure of Pulse Connect Secure appliances to untrusted networks, while monitoring systems should be configured to detect anomalous web traffic patterns that may indicate exploitation attempts. The vulnerability demonstrates characteristics consistent with ATT&CK technique T1059.007, which involves the use of script-based commands to execute malicious code, and T1203, which encompasses the use of web shell techniques for maintaining access. Regular security assessments and penetration testing should be conducted to identify potential exploitation vectors, while incident response procedures should be updated to address potential compromise scenarios involving Pulse Connect Secure appliances.