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CVE-2026-57030 — juniper / junos

Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

A Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') vulnerability in the packet forwarding engine (PFE) of Juniper Networks Junos OS on SRX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS).

As part of the stateful traffic processing on SRX Series devices flows are being established, and removed when not needed anymore. During the removal process the timeout of a flow should be set to 3 seconds and consequentially the flow should be removed shortly after. Due to a race condition occurring when setting the timeout there is a chance (the exact conditions are outside the attackers control) that the timeout is instead set to a very high value of larger than 10,000 seconds:

user@host> show security flow session | match timeout Session ID: 98784248524, Policy name: PROD-FLOW/4, HA State: Active, Timeout: 85250, Session State: Valid

This will lead to an accumulation of flows which can be observed by an ever-increasing value of invalidated sessions in the output of 'show security flow session summary':

user@host> show security flow session summary | match invalid Invalidated sessions: 216931These sessions can't be cleared manually with the 'clear security flow session' command, which will either lead to forwarding to stop (and the system needs to be manually recovered with a reboot) or to a flowd core and automatic reboot.

This issue affects Junos OS on SRX Series:

  • 24.2 versions before 24.2R2-S3,
  • 24.4 versions before 24.4R2-S1, 24.4R2-S2,
  • 25.2 versions before 25.2R1-S2, 25.2R2.

This issue does not affect releases earlier than 24.2R1;

  • Published: Jul 9, 2026
  • Updated: Jul 10, 2026
  • CVE: CVE-2026-57030
  • Severity: Medium
  • Exploit:
  • CISA KEV:

CVSS v3:

  • Severity: Medium
  • Score: 5.9
  • AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

CWEs:

Software From Fixed in
juniper / junos 24.2 24.2.x
juniper / junos 24.2-r1 24.2-r1.x
juniper / junos 24.2-r1-s1 24.2-r1-s1.x
juniper / junos 24.2-r1-s2 24.2-r1-s2.x
juniper / junos 24.2-r2 24.2-r2.x
juniper / junos 24.2-r2-s1 24.2-r2-s1.x
juniper / junos 24.2-r2-s2 24.2-r2-s2.x
juniper / junos 24.4 24.4.x
juniper / junos 24.4-r1 24.4-r1.x
juniper / junos 24.4-r1-s2 24.4-r1-s2.x
juniper / junos 24.4-r1-s3 24.4-r1-s3.x
juniper / junos 24.4-r2 24.4-r2.x
juniper / junos 25.2 25.2.x
juniper / junos 25.2-r1 25.2-r1.x
juniper / junos 25.2-r1-s1 25.2-r1-s1.x

Frequently Asked Questions

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

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Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

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