CVE-2026-57023: 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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Juniper Networks Junos OS (TCP proxy plugin on MX with SPC3 / SRX)to a version that resolves this vulnerability.Fixed in 23.4R2-S7 - Upgrade
Upgrade
Juniper Networks Junos OS (TCP proxy plugin on MX with SPC3 / SRX)to a version that resolves this vulnerability.Fixed in 24.2R2-S4 - Upgrade
Upgrade
Juniper Networks Junos OS (TCP proxy plugin on MX with SPC3 / SRX)to a version that resolves this vulnerability.Fixed in 24.4R2-S3 - Upgrade
Upgrade
Juniper Networks Junos OS (TCP proxy plugin on MX with SPC3 / SRX)to a version that resolves this vulnerability.Fixed in 25.2R2 - Upgrade
Upgrade
Juniper Networks Junos OS (TCP proxy plugin on MX with SPC3 / SRX)to a version that resolves this vulnerability.Fixed in 25.4R1
Event History
Frequently Asked Questions
What is the severity of CVE-2026-57023?
The severity of CVE-2026-57023 is high with a score of 7.5.
What type of vulnerability is CVE-2026-57023?
CVE-2026-57023 is classified as an Improper Validation of Specified Quantity in Input vulnerability.
How does CVE-2026-57023 affect systems?
CVE-2026-57023 allows an unauthenticated, network-based attacker to cause a complete Denial of Service (DoS) on affected devices.
Which devices are impacted by CVE-2026-57023?
CVE-2026-57023 affects Juniper Networks Junos OS on MX Series with SPC3 and SRX Series.
What steps should be taken to mitigate CVE-2026-57023?
To mitigate CVE-2026-57023, users should update their Junos OS to the latest patched version provided by Juniper Networks.