High [CVE-2026-57023] 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)
This high-severity Juniper Networks advisory covers CVE-2026-57023 affecting Junos OS, Junos, SRX.
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Summary
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,
This issue does not affect releases before 23.4R1.
Affected products named by the advisory: MX.
Affected products named by the advisory: MX.
- 23.4
- 24.2
- 24.4
- 25.2
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
- 23.4R2-S7
- 24.2R2-S4
- 24.4R2-S3
- 25.2R2
- 23.4R1
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
Mitigation
Upgrade to a fixed release: 23.4R2-S7, 24.2R2-S4, 24.4R2-S3, 25.2R2, 23.4R1. That is the remediation for this advisory.
The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
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