An Improper Handling of Highly Compressed Data flaw in the gRPC library used by na‑grpcd allows an authenticated, network‑based attacker to trigger a service crash by sending a specially crafted compressed gRPC request. The resulting denial of service impacts the availability of the Junos OS operating system, potentially disrupting routing, switching, and management functions without compromising confidentiality or integrity.

Juniper Networks Junos OS and Junos OS Evolved are affected. All releases prior to the patches detailed in the advisory are vulnerable. The advisory lists the following resolved release branches: Junos OS 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 all later releases; and Junos OS Evolved 23.2R2‑S7.7‑EVO, 23.4S2‑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 score of 7.1 indicates a high severity vulnerability, but the exploitability is limited to authenticated attackers due to the need for credentials to access the gRPC service. The EPSS score of 0.00411 (< 1%) indicates a very low probability of exploitation at present. The vulnerability is not listed in CISA’s KEV catalog, suggesting it is not widely exploited. The likely attack vector is from an internal network or a compromised endpoint that can authenticate to the device and send a compressed request to the gRPC extension-service. Once exploited, the device would experience a denial of service until the gRPC process is restarted or the device is rebooted.