CVE-2026-57023

Junos OS: MX with SPC3, SRX Series: A specifically malformed TCP packet causes a flowd crash

HIGH

7.5

CVSS Score

Published: July 9, 2026 at 09:06 PM UTC

Updated: October 25, 2026 at 03:10 PM UTC

1 product affected across 1 vendorJunos· also runs on 23 platforms

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Severity

HIGH7.5

Exploit prediction

EPSS 0.5%

SSVC

No known exploit

Description

An Improper Validation of Specified Quantity in Input vulnerability in the TCP proxy plugin of Juniper Networks Junos OS on MX Series with SPC3, and SRX Series allows an unauthenticated, network-based attacker to cause a complete Denial of Service (DoS). When TCP proxy is engaged in a flow session, to support ALGs, Advanced Anti-Malware, ICAP or UTM, a TCP packet with specifically malformed TCP header will cause flow processing daemon (flowd) to crash and restart. This causes a complete service outage until the system has automatically recovered. This issue affects Junos OS on MX with SPC3, and SRX Series: * 23.4 versions before 23.4R2-S7, * 24.2 versions before 24.2R2-S4, * 24.4 versions before 24.4R2-S3, * 25.2 versions before 25.2R2. This issue does not affect releases before 23.4R1.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Junos · Juniper Networks

95%

Affected range stops below 23.4R2-S7, so it looks safe — our inference, not a vendor statement

Affected range stops below 24.2R2-S4, so it looks safe — our inference, not a vendor statement

Affected range stops below 24.4R2-S3, so it looks safe — our inference, not a vendor statement

Affected range stops below 25.2R2, so it looks safe — our inference, not a vendor statement

juniper-mx-spc3 (environment) · juniper-mx240 (environment) · juniper-mx480 (environment) · juniper-mx960 (environment) · juniper-srx1500 (environment) · juniper-srx1600 (environment) · juniper-srx2300 (environment) · juniper-srx300 (environment) · juniper-srx320 (environment) · juniper-srx340 (environment) · juniper-srx345 (environment) · juniper-srx380 (environment) · juniper-srx400 (environment) · juniper-srx4100 (environment) · juniper-srx4120 (environment) · juniper-srx4200 (environment) · juniper-srx4300 (environment) · juniper-srx440 (environment) · juniper-srx4600 (environment) · juniper-srx4700 (environment) · juniper-srx5400 (environment) · juniper-srx5600 (environment) · juniper-srx5800 (environment)