Medium [CVE-2026-57027] Missing Release of Memory after Effective Lifetime vulnerability in the packet forwarding engine (pfe) of Juniper Networks Junos OS on specific EX Series devices allows an unauthenticated adjacent attacker to cause a Denial-of-Service (DoS).When sFlow is configured in a Virtual Chassis (VC) scenario with EX4100 Series or EX4400 Series devices, multicast traffic which is received on one VC member and sent out on another member leads to a memory leak and ultimately an FPC crash and restart
This medium-severity Juniper Networks advisory covers CVE-2026-57027; related products: Junos OS, Junos, EX.
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Summary
A Missing Release of Memory after Effective Lifetime vulnerability in the packet forwarding engine (pfe) of Juniper Networks Junos OS on specific EX Series devices allows an unauthenticated adjacent attacker to cause a Denial-of-Service (DoS).When sFlow is configured in a Virtual Chassis (VC) scenario with EX4100 Series or EX4400 Series devices, multicast traffic which is received on one VC member and sent out on another member leads to a memory leak and ultimately an FPC crash and restart.
The leak can be monitored by watching the continuous increase of the buffer values in the output of:
user@host> show chassis fpc This issue affects Junos OS on EX4100 Series and EX4400:
- all versions before 23.2R2-S7,
- 23.4 versions before 23.4R2-S7,
Affected products named by the advisory: EX.
Affected products named by the advisory: EX.
- * all versions before 23
Official advisory · high-confidence parse· fetched 3 months ago·verify at source
- 23.2R2-S7
- 23.4R2-S7
- 24.2R2-S4
- 24.4R2
Official advisory · high-confidence parse· fetched 3 months ago·verify at source
Mitigation
Upgrade to a fixed release: 23.2R2-S7, 23.4R2-S7, 24.2R2-S4, 24.4R2. 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 3 months ago·verify at source
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