Medium [CVE-2026-21903] Stack-based Buffer Overflow vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS
This medium-severity Juniper Networks advisory covers CVE-2026-21903; related products: Junos, Junos OS.
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Summary
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.
- all versions
Official advisory · high-confidence parse· fetched 4 months ago·verify at source
- 22.4R3-S7
- 23.2R2-S4
- 23.4R2
Official advisory · high-confidence parse· fetched 4 months ago·verify at source
Mitigation
Upgrade to a fixed release: 22.4R3-S7, 23.2R2-S4, 23.4R2. That is the remediation for this advisory.
The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.
Official advisory · high-confidence parse· fetched 4 months ago·verify at source
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