CVE-2023-22396 in Junos OS
Summary
by MITRE • 01/13/2023
An Uncontrolled Resource Consumption vulnerability in TCP processing on the Routing Engine (RE) of Juniper Networks Junos OS allows an unauthenticated network-based attacker to send crafted TCP packets destined to the device, resulting in an MBUF leak that ultimately leads to a Denial of Service (DoS). The system does not recover automatically and must be manually restarted to restore service. This issue occurs when crafted TCP packets are sent directly to a configured IPv4 or IPv6 interface on the device. Transit traffic will not trigger this issue. MBUF usage can be monitored through the use of the 'show system buffers' command. For example: user@junos> show system buffers | refresh 5 4054/566/4620 mbufs in use (current/cache/total) ... 4089/531/4620 mbufs in use (current/cache/total) ... 4151/589/4740 mbufs in use (current/cache/total) ... 4213/527/4740 mbufs in use (current/cache/total) This issue affects Juniper Networks Junos OS: 12.3 version 12.3R12-S19 and later versions; 15.1 version 15.1R7-S10 and later versions; 17.3 version 17.3R3-S12 and later versions; 18.4 version 18.4R3-S9 and later versions; 19.1 version 19.1R3-S7 and later versions; 19.2 version 19.2R3-S3 and later versions; 19.3 version 19.3R2-S7, 19.3R3-S3 and later versions prior to 19.3R3-S7; 19.4 version 19.4R2-S7, 19.4R3-S5 and later versions prior to 19.4R3-S10; 20.1 version 20.1R3-S1 and later versions; 20.2 version 20.2R3-S2 and later versions prior to 20.2R3-S6; 20.3 version 20.3R3-S1 and later versions prior to 20.3R3-S6; 20.4 version 20.4R2-S2, 20.4R3 and later versions prior to 20.4R3-S5; 21.1 version 21.1R2 and later versions prior to 21.1R3-S4; 21.2 version 21.2R1-S1, 21.2R2 and later versions prior to 21.2R3-S3; 21.3 versions prior to 21.3R3-S2; 21.4 versions prior to 21.4R3; 22.1 versions prior to 22.1R2-S1, 22.1R3; 22.2 versions prior to 22.2R1-S2, 22.2R2; 22.3 versions prior to 22.3R1-S1, 22.3R2.
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Analysis
by VulDB Data Team • 09/29/2025
This vulnerability represents a critical resource exhaustion flaw within the TCP processing stack of Juniper Networks Junos OS routing engines, specifically targeting the MBUF (memory buffer) allocation mechanism. The issue manifests as an uncontrolled consumption of system resources through crafted TCP packets that are directly sent to configured IPv4 or IPv6 interfaces on affected devices. The vulnerability operates at the network protocol level, exploiting how the routing engine handles incoming TCP connections and their associated memory management structures. Unlike typical network attacks that might target application layers, this flaw operates at the kernel level where TCP packet processing occurs, making it particularly dangerous for network infrastructure devices that must maintain continuous operation. The vulnerability is classified as an uncontrolled resource consumption issue, which aligns with CWE-400 - Uncontrolled Resource Consumption, a common weakness in network security where insufficient resource management leads to system instability. The attack vector requires only an unauthenticated network-based approach, meaning any external attacker with access to the network can potentially exploit this weakness without requiring prior authorization or credentials.
The technical implementation of this vulnerability involves the manipulation of TCP packet headers and sequence numbers to trigger a specific code path within the Junos OS TCP processing module. When the routing engine receives these crafted packets, it fails to properly release MBUF structures that are allocated during TCP connection handling, resulting in a memory leak that gradually consumes available buffer space. This process is not a simple memory leak but rather a systematic exhaustion of the MBUF pool, which is critical for network packet processing operations. The system's inability to automatically recover from this state indicates a fundamental flaw in the error handling and resource management mechanisms within the TCP stack implementation. The MBUF usage monitoring through the 'show system buffers' command reveals the progressive increase in buffer consumption, demonstrating the linear nature of the resource depletion. The specific versions affected span multiple major releases of Junos OS, indicating this is a long-standing issue that has persisted across several generations of the operating system, suggesting either inadequate testing of the TCP processing code or insufficient attention to resource management during development cycles.
The operational impact of this vulnerability extends beyond simple service disruption, as it creates a condition where the affected device becomes completely unusable for its primary function of routing network traffic. The requirement for manual system restart indicates that the DoS condition is severe enough to prevent automatic recovery mechanisms from functioning properly, potentially leading to extended network outages that can affect large portions of network infrastructure. Network administrators must monitor buffer usage continuously and be prepared to manually intervene when the system approaches critical buffer levels, which represents a significant operational burden. The vulnerability affects both IPv4 and IPv6 interfaces, increasing the attack surface and making it more difficult to defend against since network administrators cannot simply disable one protocol to mitigate the issue. Transit traffic does not trigger the vulnerability, which suggests the flaw is specifically related to packets directed to the device's own interfaces rather than packets passing through the device. This characteristic makes the vulnerability particularly concerning for devices that serve as endpoints for network traffic, such as border routers or core network devices, where direct access to the device's interfaces is often possible. The attack can be executed with minimal network resources and requires no specialized tools beyond basic packet crafting capabilities, making it accessible to a wide range of threat actors. From a cybersecurity perspective, this vulnerability represents a significant risk to network availability and can be used as part of broader attack campaigns targeting network infrastructure stability, particularly when combined with other DoS vectors. The long list of affected versions indicates that this vulnerability has been present for extended periods, suggesting that organizations may have been unknowingly exposed to this risk for years.
Mitigation strategies for this vulnerability must include immediate patching of affected systems to address the underlying TCP processing flaw in the Junos OS implementation. Juniper has released specific security advisories and patches for each affected version, and organizations should prioritize applying these updates to all impacted devices. Network segmentation and access control measures can provide temporary protection by limiting direct access to device interfaces from untrusted networks, though this approach does not eliminate the vulnerability. Monitoring systems should be configured to track MBUF usage patterns and alert administrators when usage approaches critical thresholds, enabling proactive intervention before full DoS conditions occur. Network administrators should also implement rate limiting and connection tracking mechanisms where possible to reduce the impact of potential attacks. The vulnerability's classification as a resource exhaustion issue means that traditional network security measures like firewalls or intrusion detection systems may not be effective in preventing exploitation, as the attack occurs at a low level within the TCP stack where normal network security controls may not apply. Organizations should also consider implementing redundant routing paths and failover mechanisms to ensure that network availability is maintained even if individual devices become compromised by this vulnerability. The lack of automatic recovery capability means that any defensive strategy must include manual intervention procedures and potentially automated alerting systems to ensure rapid response to buffer exhaustion conditions. This vulnerability also highlights the importance of regular security assessments and vulnerability management programs to identify and remediate similar issues before they can be exploited by malicious actors.