CVE-2026-101968 in Junos OS
Summary
by MITRE • 10/14/2026
An Integer Underflow (Wrap or Wraparound) vulnerability in the rpd process of Juniper Networks Junos OS on EX Series and MX Series, and Junos OS Evolved on ACX Series allows an unauthenticated adjacent attacker to cause heap memory disclosure and multicast join-state injection via a malformed Rosen-MVPN message.
This issue only affects platforms that support draft Rosen MVPN, such as the ACX Series, EX Series, and MX Series.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability identified in Juniper Networks Junos OS represents a critical security flaw within the routing protocol daemon process responsible for handling multicast VPN configurations. Specifically, this integer underflow occurs during the parsing of Rosen-MVPN messages on platforms that support draft Rosen MVPN standards, including the ACX Series running Junos OS Evolved and the EX and MX Series running standard Junos OS. The root cause lies in improper validation of numerical values within the message structure, allowing an attacker to manipulate integer arithmetic operations such that they wrap around or underflow rather than failing safely. This technical flaw enables an unauthenticated adjacent attacker who has network connectivity to the affected device to inject malformed packets into the control plane processing stream.
From a technical perspective, the integer underflow leads directly to heap memory disclosure and state injection vulnerabilities. When the daemon processes the crafted Rosen-MVPN message with manipulated length or offset fields, it calculates incorrect buffer sizes or access indices due to the wraparound effect. This miscalculation allows the system to read beyond intended boundaries of allocated memory structures, resulting in the leakage of sensitive internal data stored on the heap. Furthermore, the flaw permits the injection of false multicast join-state information into the routing table. By exploiting this condition, an attacker can manipulate how the router interprets membership for specific multicast groups, effectively altering the forwarding behavior without legitimate authorization or authentication credentials.
The operational impact of this vulnerability is severe due to its potential for both confidentiality breaches and integrity violations. The heap memory disclosure aspect means that sensitive information from the device's internal state could be exfiltrated by an adjacent attacker on the same network segment. This data may include routing tables, cryptographic keys, or other proprietary system details that aid in further exploitation of the network infrastructure. Simultaneously, the multicast join-state injection capability allows for traffic manipulation attacks. An adversary can cause legitimate multicast streams to be dropped or redirected, leading to denial-of-service conditions for specific applications relying on multicast delivery. Additionally, by injecting false state information, an attacker could potentially redirect sensitive data flows through a compromised node, facilitating eavesdropping or man-in-the-middle scenarios within the local network segment.
This vulnerability aligns with CWE-192, which classifies integer underflow wraparound errors that lead to out-of-bounds memory access and subsequent disclosure of information. It also relates closely to CWE-787, as the improper validation leads to accessing memory outside of intended boundaries. In terms of offensive security frameworks, this exploit scenario maps to MITRE ATT&CK technique T1046, Network Service Discovery, where an attacker probes for vulnerabilities in network services, and potentially T1530, Data from Cloud or Storage Object, if the disclosed heap data contains sensitive configuration details. The requirement for adjacency highlights that while remote exploitation over wide area networks is not possible, local network segmentation failures can expose critical infrastructure to significant risk.
Mitigation strategies must prioritize immediate patching of the Junos OS and Junos OS Evolved software on all affected platforms including ACX, EX, and MX series devices. Administrators should apply vendor-released patches that address the integer validation logic within the rpd process. Until patches are applied, network segmentation is critical; access to these management planes must be restricted via strict firewall rules or ACLs to prevent unauthenticated hosts from reaching the affected services. Additionally, enabling multicast security features such as IGMP snooping with authentication and validating incoming routing protocol messages can provide defense-in-depth layers that may mitigate the impact of malformed packet injection attempts. Regular auditing of network access controls ensures that only authorized devices can interact with critical routing protocols on adjacent segments.