CVE-2025-59962 is a medium-severity vulnerability classified under CWE-824 (Access of Uninitialized Pointer) found in the routing protocol daemon (rpd) of Juniper Networks Junos OS and Junos OS Evolved. The vulnerability specifically manifests when BGP sharding is enabled, a configuration used to improve BGP scalability by partitioning routing tables. The flaw arises when the rpd processes indirect next-hop updates triggered by changes in the Interior Gateway Protocol (IGP) routes that BGP routes depend upon. An attacker can induce indirect next-hop updates combined with timing conditions outside their control to cause the rpd process to access uninitialized memory pointers, leading to a crash and subsequent restart of the daemon. This results in a Denial of Service (DoS) condition affecting routing stability. The vulnerability can be exacerbated by continuous IGP route churn, which forces repeated route re-resolution and increases the likelihood of triggering the crash. Affected Junos OS versions include all releases before 21.4R3-S6, and various releases up to 23.2R2, with similar version ranges for Junos OS Evolved. Versions prior to 21.3R1 are not vulnerable. The CVSS v3.1 base score is 5.3, reflecting a network attack vector requiring high attack complexity but no privileges or user interaction. No public exploits or active exploitation have been reported to date. The vulnerability impacts the availability of routing services, potentially disrupting network operations in environments using Juniper routers with BGP sharding enabled.

For European organizations, this vulnerability poses a risk of network instability and service disruption due to potential Denial of Service conditions on critical routing infrastructure. Organizations operating Juniper routers with Junos OS or Junos OS Evolved versions affected by this vulnerability and configured with BGP sharding are at risk of rpd crashes triggered by malicious or accidental IGP route churn. This can lead to intermittent or prolonged loss of routing capabilities, impacting business continuity, especially for ISPs, cloud providers, financial institutions, and enterprises relying on Juniper networking equipment for critical connectivity. The impact is primarily on availability, with no direct confidentiality or integrity compromise reported. However, routing outages can indirectly affect data flows and service delivery. Given the medium CVSS score and the complexity of exploitation, the threat is moderate but should not be underestimated in environments with high routing churn or targeted attacks aiming to disrupt network operations.

1. Upgrade affected Junos OS and Junos OS Evolved devices to the fixed versions as soon as patches become available from Juniper Networks. 2. If immediate patching is not feasible, consider disabling BGP sharding temporarily or reconfiguring routing policies to minimize indirect next-hop updates and IGP route churn. 3. Monitor routing protocol daemon (rpd) stability and logs for signs of crashes or restarts, especially in environments with frequent IGP route changes. 4. Implement network segmentation and rate limiting to reduce the potential for an attacker to induce continuous IGP route churn. 5. Employ anomaly detection systems to identify unusual routing updates or patterns that could trigger the vulnerability. 6. Coordinate with Juniper support for guidance on interim mitigations and best practices tailored to your network environment. 7. Maintain an up-to-date inventory of Juniper devices and their software versions to prioritize patching efforts effectively.