CVE-2026-57023Network attack vector

Unauthenticated service outage via malformed TCP headers

Published Jul 9, 2026 · Updated Jul 9, 2026

Improper input validation in Junos OS on MX with SPC3 and SRX Series allows remote attackers to interrupt service via TCP traffic. The TCP proxy plugin fails to validate a quantity in a crafted TCP header before flowd processes it, causing the daemon to crash and restart. No authentication is required, but the packet must reach a flow using TCP proxy for an ALG, Advanced Anti-Malware, ICAP, or UTM; service remains unavailable until automatic recovery.

CVSS severity8.7
High
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Junos OS on MX with SPC3 and SRX Series allows remote attackers to interrupt service via TCP traffic. The TCP proxy plugin fails to validate a quantity in a crafted TCP header before flowd processes it, causing the daemon to crash and restart. No authentication is required, but the packet must reach a flow using TCP proxy for an ALG, Advanced Anti-Malware, ICAP, or UTM; service remains unavailable until automatic recovery.

The record

CVE
CVE-2026-57023
Published
Jul 9, 2026
Updated
Jul 9, 2026
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-1284, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 9, 2026Record 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=23.4 <23.4R2-S7
  2. Affected versionversion=24.2 <24.2R2-S4
  3. Affected versionversion=24.4 <24.4R2-S3
  4. Affected versionversion=25.2 <25.2R2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=23.4 <23.4R2-S7; version=24.2 <24.2R2-S4; version=24.4 <24.4R2-S3; version=25.2 <25.2R2

Published CVSS scores

7.5Juniper NetworksCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7Juniper NetworksCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L

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-1284Improper Validation of Specified Quantity in Input
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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