CVE-2024-21601Network attack vector

Sustained service interruption via TCP-event queue race

Published Jan 12, 2024 · Updated Nov 14, 2024

Race condition in flowd in Juniper Networks Junos OS on SRX Series allows remote attackers to crash the daemon through TCP traffic. Two flowd threads can process the same TCP-event queue concurrently without proper synchronization, causing the daemon to crash. One thread cannot be triggered externally, so exploitation depends on attacker-uncontrolled timing; repeated crashes sustain the service interruption.

CVSS severity5.9
Medium
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in flowd in Juniper Networks Junos OS on SRX Series allows remote attackers to crash the daemon through TCP traffic. Two flowd threads can process the same TCP-event queue concurrently without proper synchronization, causing the daemon to crash. One thread cannot be triggered externally, so exploitation depends on attacker-uncontrolled timing; repeated crashes sustain the service interruption.

The record

CVE
CVE-2024-21601
Published
Jan 12, 2024
Updated
Nov 14, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-362, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 12, 2024CVE publishedPublication date reported by the CVE source.
  2. Nov 14, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=21.2 <21.2R3-S5
  2. Affected versionversion=21.3 <21.3R3-S5
  3. Affected versionversion=21.4 <21.4R3-S4
  4. Affected versionversion=22.1 <22.1R3-S3
  5. Affected versionversion=22.2 <22.2R3-S1
  6. Affected versionversion=22.3 <22.3R2-S2, 22.3R3
  7. Affected versionversion=22.4 <22.4R2-S1, 22.4R3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=21.2 <21.2R3-S5; version=21.3 <21.3R3-S5; version=21.4 <21.4R3-S4; version=22.1 <22.1R3-S3; version=22.2 <22.2R3-S1; version=22.3 <22.3R2-S2, 22.3R3; version=22.4 <22.4R2-S1, 22.4R3

Published CVSS scores

5.9Juniper NetworksCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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