dbcve.org
JunosOperating system · Juniper

CVE-2026-57023

HIGH · 7.5 CVSS v3.1 Published 2026-07-09
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click 6 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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,  * 24.4 versions before 24.4R2-S3, * 25.2 versions before 25.2R2. This issue does not affect releases before 23.4R1.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A vulnerability in the TCP proxy plugin of Juniper Junos OS on MX Series (with SPC3) and SRX Series allows an unauthenticated remote attacker to cause complete DoS. When TCP proxy is engaged to support ALGs, Advanced Anti-Malware, ICAP, or UTM, a specifically malformed TCP header triggers a crash in the flowd (flow processing daemon), causing service outage until auto-recovery.

MitigationApply the vendor-supplied software patches (23.4R2-S7, 24.2R2-S4, 24.4R2-S3, or 25.2R2 or later) to affected MX and SRX devices. Disable unused ALGs/UTM features if patching is delayed.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
JunosOperating system
Affected:= 23.4= 24.2= 24.4= 25.2

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify device model
    Run 'show chassis hardware' or 'show system information' to confirm if the device is an MX Series (with SPC3) or SRX Series
    Affected if Device is NOT an MX Series or SRX Series (other models are not affected)
  2. Check Junos OS version
    Run 'show version' to display the installed Junos OS version
    Affected if Version matches 23.4, 24.2, 24.4, or 25.2 (or falls within these release trains)
  3. Verify TCP proxy is engaged for ALGs
    Run 'show security alg' to list enabled Application Layer Gateways
    Affected if Any ALG (e.g., FTP, HTTP, SMTP, DNS) is enabled - TCP proxy is engaged when ALGs are active
  4. Verify UTM/Advanced Anti-Malware is enabled
    Run 'show security utm' and 'show security anti-virus' to check UTM and Advanced Anti-Malware status
    Affected if UTM or Advanced Anti-Malware profile is attached to a security policy - this engages TCP proxy
  5. Verify ICAP redirect is configured
    Run 'show configuration security nat source' and look for 'icap' or 'redirect' under UTM settings
    Affected if ICAP redirection is configured - this engages TCP proxy

Device is affected if it is an MX Series (with SPC3) or SRX Series, runs a vulnerable Junos version (23.4, 24.2, 24.4, or 25.2), AND has TCP proxy engaged via any enabled ALG, UTM, Advanced Anti-Malware, or ICAP configuration.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the vendor-supplied software patches (23.4R2-S7, 24.2R2-S4, 24.4R2-S3, or 25.2R2 or later) to affected MX and SRX devices. Disable unused ALGs/UTM features if patching is delayed.

Recommended fix High confidence

23.4R2-S7, 24.2R2-S4, 24.4R2-S3, or 25.2R2 (depending on which branch you are on)

  1. 1. Identify the current Junos OS version running on the device using 'show version'
  2. 2. Determine which branch (23.4, 24.2, 24.4, or 25.2) the current version belongs to
  3. 3. Download the appropriate fixed Junos OS release for the device platform (MX with SPC3 or SRX Series): for 23.4 branch use 23.4R2-S7 or later, for 24.2 branch use 24.2R2-S4 or later, for 24.4 branch use 24.4R2-S3 or later, for 25.2 branch use 25.2R2 or later
  4. 4. Schedule a maintenance window as the upgrade will cause a system reboot
  5. 5. Backup the current configuration using 'request system configuration rescue save'
  6. 6. Transfer the Junos upgrade package to the device using SCP or FTP
  7. 7. Install the upgrade using 'request system software add <package-name> reboot'
  8. 8. After the device reboots, verify the new version using 'show version'
Caveat Standard Junos upgrade may cause temporary service disruption; ensure configuration compatibility review before upgrading across major releases

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Junos Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing8.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,800
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,080.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-57023 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-57023 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data