The reported flaw is a stack‑based buffer overflow (CWE‑121) in the cfmd process of Juniper Networks Junos OS on MX Series and Junos OS Evolved on PTX Series platforms. An unauthenticated attacker on an adjacent network can send a specially crafted CFM message to a configured down‑MEP with enhanced CFM mode enabled, causing the vulnerable process to execute arbitrary code as the root user or trigger a denial‑of‑service condition. This results in full system compromise or service interruption for the affected device.

The vulnerability affects devices running Junos OS and Junos OS Evolved. On MX Series routers, any Junos OS version up to and including 26.4R1 and the earlier releases listed (23.2R2‑S7.7 23.4R2‑S8.13, 24.2R2‑S5.5, etc.) are impacted. On PTX Series platforms, the same applies to Junos OS Evolved releases up to 26.4R1‑EVO and the earlier respins such as 23.2R2‑S7.7‑EVO, 23.4R2‑S8.11‑EVO, 24.2R2‑S5.6‑EVO, etc. All subsequent releases beyond those specifically listed are reported to have the fix.

The CVSS v3 base score of 8.7 indicates a high severity vulnerability. The EPSS score of 0.00325 (<1%) indicates a very low exploitation probability, but the flaw still allows unauthenticated exploitation by sending a crafted CFM message over the local network to a configured down‑MEP with enhanced CFM mode enabled. The vulnerability is not yet listed in CISA KEV. Attackers could remotely gain root‑level privileges or disrupt service, making immediate patching essential.