CVE-2026-57027: junos — Fix

Description

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, * 24.2 versions before 24.2R2-S4, * 24.4 versions before 24.4R2.

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CVSS v3.1 Score

6.5

MEDIUM

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0027

Probability of exploitation

0.19%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-401 CWE-401

Affected Products

Vendor	Product	Versions
juniper	junos	< 23.2
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	ex4100	All
juniper	ex4100-f	All
juniper	ex4100-h	All
juniper	ex4100-h-12t	All
juniper	ex4400	All

References

Advisories & Patches

https://supportportal.juniper.net/JSA110087

Frequently Asked Questions

What is CVE-2026-57027? +

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, * 24.2 versions before 24.2R2-S4, * 24.4 versions before 24.4R2. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-57027? +

CVE-2026-57027 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0027, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-57027? +

CVE-2026-57027 affects products from juniper, specifically: ex4100, ex4100-f, ex4100-h, ex4100-h-12t, ex4400, junos. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-57027? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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