CVE-2023-28985 in Junos OS
Summary
by MITRE • 07/14/2023
An Improper Validation of Syntactic Correctness of Input vulnerability in Intrusion Detection and Prevention (IDP) of Juniper Networks SRX Series and MX Series allows an unauthenticated, network-based attacker to cause Denial of Service (DoS). Continued receipt of this specific packet will cause a sustained Denial of Service condition.
On all SRX Series and MX Series platforms, where IDP is enabled and a specific malformed SSL packet is received, the SSL detector crashes leading to an FPC core.
This issue affects Juniper Networks SRX Series and MX Series prior to SigPack 3598.
In order to identify the current SigPack version, following command can be used:
user@junos# show security idp security-package-version
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Analysis
by VulDB Data Team • 07/14/2023
This vulnerability represents a critical denial of service weakness in Juniper Networks SRX and MX series devices where the intrusion detection and prevention system fails to properly validate the syntactic correctness of incoming SSL packets. The flaw exists within the SSL detector module that processes network traffic, specifically when malformed SSL packets are received without proper authentication. This improper input validation creates a condition where an attacker can exploit the system by sending specifically crafted packets that trigger a crash in the Flexible Packet Core (FPC) component, leading to sustained service disruption. The vulnerability is particularly concerning because it requires no authentication credentials to exploit, making it accessible to any network-based attacker who can reach the affected device. The issue manifests across all SRX and MX series platforms where IDP functionality is enabled, and the problem specifically occurs when the SSL detector encounters malformed packets that it cannot properly parse or handle, resulting in system instability and complete service outage.
The technical implementation of this vulnerability stems from inadequate input sanitization within the SSL protocol handling mechanism of the IDP system. When a malformed SSL packet is received, the system's SSL detector module attempts to process the packet without sufficient validation checks to ensure syntactic correctness before proceeding with deeper parsing operations. This lack of proper validation allows the malformed packet to trigger an exception or memory corruption condition that ultimately causes the FPC core to crash, leading to the complete denial of service. The vulnerability is categorized under CWE-20, Improper Input Validation, which specifically addresses weaknesses where input is not properly validated for syntactic correctness, and can be mapped to ATT&CK technique T1499.1 for network denial of service attacks. The crash occurs at the hardware level within the FPC, which is responsible for packet processing and forwarding, making the impact particularly severe as it affects the core functionality of the device.
The operational impact of this vulnerability extends beyond simple service disruption to create sustained denial of service conditions that can persist as long as the malformed packets continue to be received. Network administrators face the challenge of maintaining service availability when attackers can leverage this vulnerability to continuously disrupt network operations without requiring any privileged access or authentication credentials. The affected platforms include all SRX and MX series devices running software versions prior to SigPack 3598, which creates a significant attack surface across enterprise and service provider networks. Organizations utilizing Juniper's IDP functionality are particularly vulnerable, as the system's ability to detect and prevent intrusions is compromised by this very weakness, potentially allowing attackers to not only disrupt services but also to mask other malicious activities by creating a distraction through sustained denial of service attacks. The FPC core crash represents a fundamental system failure that requires manual intervention or device reboot to restore normal operations, creating extended downtime periods that can significantly impact business continuity and network availability.
Mitigation strategies for this vulnerability require immediate implementation of software updates to reach SigPack 3598 or later versions where the input validation has been corrected. Network administrators should prioritize patching affected devices as soon as possible, particularly those with IDP enabled and exposed to untrusted network segments. Additional protective measures include implementing network access controls to limit exposure of affected devices to untrusted traffic, configuring firewall rules to filter out suspicious SSL traffic patterns, and monitoring network logs for signs of exploitation attempts. Organizations should also consider temporarily disabling IDP functionality on affected devices until patches can be properly deployed and tested in their environment. The remediation process must include thorough testing of patches in non-production environments to ensure compatibility with existing network configurations and to prevent unintended side effects on other security features. Security teams should also implement network monitoring solutions to detect and alert on patterns consistent with this specific vulnerability, enabling rapid response to potential exploitation attempts and providing valuable intelligence for incident response activities.