An improper validation of the specified quantity in input data within the l2ald process allows an adjacent attacker to send a crafted ICCP MC‑LAG message that causes the switch to crash, resulting in denial of service. The vulnerability is a classic input validation flaw (CWE‑1284) that can lead to complete service interruption on the affected device. Because it targets internal MC‑LAG communication, an attacker must be on the same local network segment or have connectivity to the MC‑LAG peer to trigger the exploit.

Juniper Networks Junos OS and Junos OS Evolved are affected. All releases prior to the security‑updated versions listed in the advisory are vulnerable. For Junos OS, this includes versions earlier than 23.2R2‑S7.7, 23.4R2‑S8.13, 24.2R2‑S5.5, 24.4R2‑S5, 25.2R2‑S2, 25.4R1‑S3, 25.4R2, 26.2R1‑S2, 26.2R2, 26.4R1 and for Junos OS Evolved, versions earlier than 23.2R2‑S7.7‑EVO, 23.4R2‑S8.11‑EVO, 24.2R2‑S5.6‑EVO, 24.4R2‑S5‑EVO, 25.2R2‑S2‑EVO, 25.2X100‑D35‑EVO, 25.4R1‑S3‑EVO, 25.4R2‑EVO, 25.4X300‑D40‑EVO, 26.2R1‑S2‑EVO, 26.2R2‑EVO, 26.4R1‑EVO and all subsequent releases.

The CVSS base score of 7.1 reflects a high impact denial of service with difficulty to exploit. The EPSS score is unavailable, indicating no public data on exploitation frequency, and the vulnerability is not listed in CISA KEV. An attacker would need local network proximity to construct and send the malicious MC‑LAG message, so the threat is confined to networks where MC‑LAG traffic is allowed. Given the lack of documented exploits, the risk is moderate but the potential for service disruption in production or critical network environments is significant, warranting prompt remediation.