High [CVE-2026-21918] Double Free vulnerability in the flow processing daemon (flowd) of Juniper Networks Junos OS on SRX and MX Series
This high-severity Juniper Networks advisory covers CVE-2026-21918 affecting Junos, Junos OS, SRX.
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Summary
A Double Free vulnerability in the flow processing daemon (flowd) of Juniper Networks Junos OS on SRX and MX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS). On all SRX and MX Series platforms, when during TCP session establishment a specific sequence of packets is encountered a double free happens.
This causes flowd to crash and the respective FPC to restart.
This issue affects Junos OS on SRX and MX Series:
- all versions before 22.4R3-S7,
- 23.2 versions before 23.2R2-S3,
- 23.4 versions before 23.4R2-S4,
Affected products named by the advisory: MX.
- all versions
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
- 22.4R3-S7
- 23.2R2-S3
- 23.4R2-S4
- 24.2R2
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
Mitigation
Upgrade to a fixed release: 22.4R3-S7, 23.2R2-S3, 23.4R2-S4, 24.2R2. 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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