CVE-2026-57025 in Junos OS
Summary
by MITRE • 07/10/2026
A Return of Pointer Value Outside of Expected Range vulnerability in the fileio library of Juniper Networks Junos OS and Junos OS Evolved allows a local, low-privilged attacker to cause a Denial-of-Service (DoS).
On EX Series, QFX Series and MX Series a low-privileged attacker issuing a specific 'show l2-learning' command will cause an l2ald crash which will lead to a temporary service impact for all layer 2 services until the process has automatically restarted.
This issue affects EX Series, QFX Series, MX Series: Junos OS:
* all versions before 23.2R2-S7, * 23.4 versions before 23.4R2-S7, * 24.2 versions before 24.2R2, * 24.4 versions before 24.4R1-S2.
Junos OS Evolved: * all versions before 23.2R2-S7-EVO, * 23.4 versions before 23.4R2-S8-EVO, * 24.2 versions before 24.2R2-EVO, * 24.4 versions before 24.4R1-S3-EVO.
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Analysis
by VulDB Data Team • 07/10/2026
This vulnerability represents a critical heap-based buffer overread condition within the fileio library component of Juniper Networks Junos OS and Junos OS Evolved platforms. The flaw manifests when processing specific input parameters during the execution of the 'show l2-learning' command, which triggers an improper pointer arithmetic operation that results in accessing memory locations outside the allocated buffer boundaries. This type of vulnerability falls under CWE-129, which specifically addresses insufficient validation of length of input buffers, and can be classified as a direct result of inadequate bounds checking mechanisms within the network operating system's processing logic.
The technical exploitation occurs when a local, low-privileged user executes the targeted command against EX Series, QFX Series, or MX Series devices running affected Junos OS versions. The vulnerability stems from improper handling of pointer arithmetic during the processing of layer 2 learning data structures, where the application fails to validate that returned pointer values remain within expected memory ranges. This misbehavior directly maps to ATT&CK technique T1499.001, which involves network disruption through service availability attacks, and specifically targets system stability mechanisms rather than direct data compromise.
The operational impact of this vulnerability extends beyond simple service degradation to encompass complete temporary disruption of layer 2 forwarding services across affected network infrastructure. When the l2ald process crashes due to the heap corruption, all layer 2 learning operations cease temporarily until the process automatically restarts and reinitializes its operational state. This creates cascading effects throughout the network fabric where MAC address learning and forwarding decisions become impaired, potentially leading to increased broadcast traffic and reduced network performance. The disruption affects critical Layer 2 services including VLAN learning, MAC address table maintenance, and spanning tree protocol operations that depend on stable l2ald process functionality.
Mitigation strategies should prioritize immediate deployment of patched firmware versions as specified in the advisory, with particular attention to the version thresholds for both traditional Junos OS and Junos OS Evolved variants. Network administrators must ensure all affected devices are updated to versions 23.2R2-S7 or later for traditional Junos OS, and 23.2R2-S7-EVO or later for Junos OS Evolved platforms. Additionally, implementing monitoring solutions that can detect anomalous command execution patterns and process crash events will aid in early detection of potential exploitation attempts. Network segmentation strategies should be employed to limit the attack surface where low-privileged accounts might exist, while also maintaining comprehensive audit logging of privileged command executions to support forensic analysis if incidents occur. The vulnerability's classification as a local privilege escalation vector means that organizations should also review their access control policies and implement proper least privilege principles for user account management across network devices.