Medium [CVE-2026-57020] Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (pfe) of Juniper Networks Junos OS on QFX10000 Series allows an unauthenticated, adjacent attacker to cause a Denial-of-Service (DoS)
This medium-severity Juniper Networks advisory covers CVE-2026-57020 affecting Junos OS, Junos.
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Summary
An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (pfe) of Juniper Networks Junos OS on QFX10000 Series allows an unauthenticated, adjacent attacker to cause a Denial-of-Service (DoS).
On all QFX10000 platforms in an EVPN-VxLAN scenario, if an attacker sends IPv6 multicast traffic and these packets reach the non-IRB interface of a spine switch it floods the packet to other spines and all Ethernet Segment Identifier (ESI) leaf switches.
This flooding causes the packet to be forwarded in a endless loop, which can lead to saturation of the involved links and in turn impact to legitimate traffic.
This issue affects Junos OS on QFX10000 Series:
- all versions before 23.2R2-S7,
- 23.4 versions before 23.4R2-S8,
- * all versions before 23
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
- 23.2R2-S7
- 23.4R2-S8
- 24.2R2-S4
- 24.4R2-S4
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
Mitigation
Upgrade to a fixed release: 23.2R2-S7, 23.4R2-S8, 24.2R2-S4, 24.4R2-S4. 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 2 months ago·verify at source
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