CVE-2026-21903
Severity CVSS v4.0:
HIGH
Type:
CWE-121
Stack-based Buffer Overflow
Publication date:
15/01/2026
Last modified:
15/01/2026
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).<br />
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Subscribing to telemetry sensors at scale causes all FPC connections to drop, resulting in an FPC crash and restart.<br />
The issue was not seen when YANG packages for the specific sensors were installed. <br />
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This issue affects Junos OS: <br />
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* all versions before 22.4R3-S7,<br />
* 23.2 version before 23.2R2-S4,<br />
* 23.4 versions before 23.4R2.
Impact
Base Score 4.0
7.10
Severity 4.0
HIGH
Base Score 3.x
6.50
Severity 3.x
MEDIUM