CVE-2022-22231 is a high-severity vulnerability identified in the Packet Forwarding Engine (PFE) component of Juniper Networks Junos OS, specifically affecting SRX Series devices running version 21.4 prior to 21.4R1-S2 and 21.4R2. The vulnerability arises from an unchecked return value leading to a NULL pointer dereference (classified under CWE-690). When Unified Threat Management (UTM) features Enhanced Content Filtering (CF) and AntiVirus (AV) are enabled simultaneously, processing certain valid transit traffic can cause the PFE to crash and subsequently restart. This results in a denial of service (DoS) condition. The vulnerability is exploitable remotely by an unauthenticated attacker over the network, requiring no user interaction, making it particularly dangerous in exposed environments. The flaw does not impact versions prior to 21.4R1, and no known exploits have been reported in the wild as of the published date. The CVSS v3.1 base score is 7.5, reflecting high severity due to the ease of exploitation (network vector, no privileges or user interaction required) and the impact limited to availability (no confidentiality or integrity loss). The vulnerability is rooted in improper error handling within the PFE code when both UTM CF and AV modules are active, causing the system to mishandle certain traffic flows and crash the forwarding engine, disrupting network operations.

For European organizations, particularly those relying on Juniper SRX Series firewalls and security gateways with Junos OS 21.4, this vulnerability poses a significant risk of network disruption. The denial of service caused by the PFE crash can lead to temporary loss of firewall and routing capabilities, impacting business continuity, especially in environments where these devices serve as critical perimeter defenses or core network components. Organizations using UTM features with Enhanced Content Filtering and AntiVirus enabled simultaneously are at heightened risk. The disruption can affect availability of services, potentially causing downtime for internal and external communications, and may hinder incident response capabilities. Given the unauthenticated and network-based nature of the exploit, attackers could trigger DoS remotely without needing access credentials, increasing the threat surface. This could be exploited in targeted attacks against critical infrastructure, financial institutions, telecommunications providers, or government networks within Europe, where Juniper devices are commonly deployed. The lack of confidentiality or integrity impact limits data breach concerns but does not diminish the operational impact of service outages.

European organizations should prioritize upgrading affected Junos OS SRX Series devices to versions 21.4R1-S2, 21.4R2, or later where the vulnerability is patched. Until patches are applied, administrators should consider temporarily disabling either Enhanced Content Filtering or AntiVirus UTM features if both are enabled simultaneously, to prevent triggering the vulnerability. Network segmentation and strict access controls should be enforced to limit exposure of vulnerable devices to untrusted networks. Monitoring network traffic for unusual patterns that could trigger the PFE crash is advisable. Additionally, implementing rate limiting or filtering of suspicious transit traffic may reduce the risk of exploitation. Organizations should maintain up-to-date inventories of Juniper devices and their firmware versions to identify vulnerable systems quickly. Regular backups and failover configurations can help mitigate the operational impact of potential DoS events. Close coordination with Juniper Networks support and subscribing to security advisories will ensure timely awareness of patches and mitigation guidance.