CVE-2026-21918

published 2026-01-15

CVE-2026-21918: A Double Free vulnerability in the flow processing daemon (flowd) of Juniper Networks Junos OS on SRX and MX Series allows an unauthenticated, network-based…

Priority P3 48 high 7.5 CVSS 3.1

AV N AC L PR N UI N S U C N I N A H

A Double Free vulnerability in the flow processing daemon (flowd) of Juniper Networks Junos OS on SRX and MX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS). On all SRX and MX Series platforms, when during TCP session establishment a specific sequence of packets is encountered a double free happens. This causes flowd to crash and the respective FPC to restart.

This issue affects Junos OS on SRX and MX Series:

* all versions before 22.4R3-S7,
* 23.2 versions before 23.2R2-S3,
* 23.4 versions before 23.4R2-S4,
* 24.2 versions before 24.2R2.

Affected

12 ranges

Vendor	Product	Version range	Fixed in
juniper	junos	< 22.4	22.4
juniper	junos	—	—
juniper	junos	—	—
juniper	junos	—	—
juniper	junos	—	—
juniper	junos_os	—	—
juniper	mx_series	—	—
juniper	srx_series	—	—
juniper_networks	junos_os	< 22.4R3-S7	22.4R3-S7
juniper_networks	junos_os	>= 23.2 < 23.2R2-S3	23.2R2-S3
juniper_networks	junos_os	>= 23.4 < 23.4R2-S4	23.4R2-S4
juniper_networks	junos_os	>= 24.2 < 24.2R2	24.2R2

CVSS provenance

nvd v3.1 7.5 HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd v4.0 8.7 HIGH CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:A/V:X/RE:M/U:X

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