CVE-2026-57023

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

Assigner: juniper
Reserved: 23.06.2026 Published: 09.07.2026 Updated: 10.07.2026

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.

Metrics

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS Score: 7.5

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	None
Privileges Required	None	Integrity Impact	None
User Interaction	None	Availability Impact	High

CVSS 3.1

CVSS Vector: 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/AU:Y/R:A/RE:M
CVSS Score: 8.7

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	None	Confidentiality	None
Attack Complexity	Low	Integrity	None	Integrity	None
Attack Requirements	None	Availability	High	Availability	Low
Privileges Required	None
User Interaction	None

CVSS 4.0

Product Status

Vendor	Juniper Networks
Product	Junos OS
Versions	Default: unaffected affected from 23.4 to 23.4R2-S7 (excl.) affected from 24.2 to 24.2R2-S4 (excl.) affected from 24.4 to 24.4R2-S3 (excl.) affected from 25.2 to 25.2R2 (excl.)

Vendor

Juniper Networks

Product

Junos OS

Versions

Default: unaffected

affected from 23.4 to 23.4R2-S7 (excl.)
affected from 24.2 to 24.2R2-S4 (excl.)
affected from 24.4 to 24.4R2-S3 (excl.)
affected from 25.2 to 25.2R2 (excl.)

Exploits

Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

Workarounds

There are no known workarounds for this issue.

Solutions

The following software releases have been updated to resolve this specific issue: 23.4R2-S7, 24.2R2-S4, 24.4R2-S3, 25.2R2, 25.4R1, and all subsequent releases.

References

Problem Types

CWE-1284 Improper Validation of Specified Quantity in Input CWE

CVE-2026-57023 PUBLISHED