Vulnerability · Published Jan 15, 2026 · Assigned by juniper

CVE-2026-21903Junos OS: Subscribing to telemetry sensors at scale causes all FPCs to crash

Medium 6.5

In plain English

A medium-severity stack buffer overflow in Junos OS from Juniper Networks. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 34% of all known vulnerabilities).

Severity (CVSS 3.1)6.5Medium

Exploit odds (30 days)0.4%top 65.6% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

A Stack-based Buffer Overflow vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS allows a network-based attacker, authenticated with low privileges to cause a Denial-of-Service (DoS). 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. This issue affects Junos OS: * all versions before 22.4R3-S7, * 23.2 version before 23.2R2-S4, * 23.4 versions before 23.4R2.

Affected products (as reported)

Vendor	Product	Versions
Juniper Networks	Junos OS	0 – before 22.4R3-S723.2 – before 23.2R2-S423.4 – before 23.4R2

Weakness: CWE-121 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

References

https://supportportal.juniper.net/JSA106022 vendor-advisory
https://kb.juniper.net/JSA106022 vendor-advisory