Juniper Junos OS TCP Proxy Plugin DoS before 23.4, 24.2, 24.4, 25.2
CVE-2026-57023 Published on July 9, 2026
Junos OS: MX with SPC3, SRX Series: A specifically malformed TCP packet causes a flowd crash
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.
Vulnerability Analysis
CVE-2026-57023 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.
Weakness Type
Improper Validation of Specified Quantity in Input
The product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties.
Products Associated with CVE-2026-57023
Want to know whenever a new CVE is published for Juniper Networks Junos? stack.watch will email you.
Affected Versions
Juniper Networks Junos OS:- Version 23.4 and below 23.4R2-S7 is affected.
- Version 24.2 and below 24.2R2-S4 is affected.
- Version 24.4 and below 24.4R2-S3 is affected.
- Version 25.2 and below 25.2R2 is affected.