Product:
Junos OS
Summary
A Stack-based Buffer Overflow vulnerability in the Packet Forwarding Engine of Juniper Networks Junos OS allows a network-based attacker, authenticated with low privileges to cause a Denial-of-Service. Subscribing to telemetry sensors at scale causes all FPC connections to drop, resulting in an FPC crash and restart. The issue was not seen when YANG packages for the specific sensors were installed.
Details
| Severity | Base Score | CVE |
|---|---|---|
| HIGH | 7.1 | CVE-2026-21903 |
Exploitation
An attacker can exploit this vulnerability by subscribing to telemetry sensors at scale, which leads to the dropping of all FPC connections. This results in a crash and restart of the FPC, causing a Denial-of-Service condition. The attacker only needs low privileges to initiate this action, making it relatively easy to exploit.
Affected Products
- All versions before 22.4R3-S7
- 23.2 version before 23.2R2-S4
- 23.4 versions before 23.4R2
Mitigation
To mitigate this vulnerability, it is recommended to upgrade to the latest versions of Junos OS that are not affected by this issue. Additionally, monitoring and limiting the subscription to telemetry sensors can help prevent exploitation until an upgrade can be performed.