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JunosOperating system · Juniper

CVE-2026-57026

HIGH · 7.5 CVSS v3.1 Published 2026-07-09
Fix available
A fix is available. Upgrade to 23.2 or later.
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 Syntactic Correctness of Input vulnerability in the SIP plugin of Juniper Networks Junos OS on MX Series with SPC3 and SRX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS).If the SIP ALG is enabled on an affected device, the processing of a malformed SIP invite packet will cause a flow processing daemon (flowd) crash and restart. This leads to a complete service outage until the system has automatically recovered. This issue affects Junos OS on MX Series with SPC3 and SRX Series: * all versions before 23.2R2-S7, * 23.4 versions before 23.4R2-S8, * 24.2 versions before 24.2R2-S5, * 24.4 versions before 24.4R2-S4, * 25.2 versions before 25.2R2, * 25.4 versions before 25.4R1-S2.

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 SIP ALG plugin of Juniper Networks Junos OS on MX Series (with SPC3) and SRX Series allows an unauthenticated remote attacker to cause denial of service by sending a malformed SIP invite packet. The attack triggers a flowd daemon crash and restart, resulting in complete service outage until auto-recovery.

MitigationDisable the SIP ALG if not required, or upgrade Junos OS to a patched version (23.2R2-S7, 23.4R2-S8, 24.2R2-S5, 24.4R2-S4, 25.2R2, or 25.4R1-S2 or later) to remediate this vulnerability.

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:< 23.2= 23.2= 23.4= 24.2= 24.4= 25.2= 25.4

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 check device model to confirm it is an MX Series (with SPC3) or SRX Series device
    Affected if Device is not an MX Series or SRX Series, then not affected by this specific vulnerability
  2. Check installed Junos OS version
    Run 'show version' to obtain the Junos OS version number
    Affected if Version matches or falls within the affected list: < 23.2, 23.2, 23.4, 24.2, 24.4, 25.2, or 25.4
  3. Verify SIP ALG is enabled
    Run 'show security alg status' or 'show configuration security alg sip' to check if the SIP Application Layer Gateway is enabled
    Affected if SIP ALG is enabled and running on the device, making it vulnerable to malformed SIP packets
  4. Check for flowd daemon crashes
    Run 'show system core-dumps' or check '/var/log/messages' for flowd or crash-related entries, particularly around SIP processing
    Affected if Recent flowd crashes are found with SIP invite packet patterns, indicating potential exploitation

Device is affected if it is an MX Series or SRX Series running an affected Junos version with SIP ALG enabled, and the vulnerability can be triggered by malformed SIP invite packets causing flowd crashes.

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
Upgrade available Upgrade to 23.2 or later
Fixed in 23.2
Interim mitigation

Disable the SIP ALG if not required, or upgrade Junos OS to a patched version (23.2R2-S7, 23.4R2-S8, 24.2R2-S5, 24.4R2-S4, 25.2R2, or 25.4R1-S2 or later) to remediate this vulnerability.

Recommended fix High confidence

23.2R2-S7, 23.4R2-S8, 24.2R2-S5, 24.4R2-S4, 25.2R2, or 25.4R1-S2 (depending on which branch you are on)

  1. 1. Identify the current Junos OS version on the MX Series (with SPC3) or SRX Series device using 'show version'
  2. 2. If SIP ALG is enabled and cannot upgrade immediately, disable SIP ALG as a mitigation: Enter configuration mode and run 'set security alg sip disable', then commit the change
  3. 3. Plan upgrade to a fixed release: For 23.2 branch, upgrade to 23.2R2-S7 or later; for 23.4 branch, upgrade to 23.4R2-S8 or later; for 24.2 branch, upgrade to 24.2R2-S5 or later; for 24.4 branch, upgrade to 24.4R2-S4 or later; for 25.2 branch, upgrade to 25.2R2 or later; for 25.4 branch, upgrade to 25.4R1-S2 or later
  4. 4. Download the appropriate Junos OS upgrade package from the Juniper Networks support portal
  5. 5. Upload the upgrade package to the device and initiate the upgrade following standard Junos upgrade procedures
  6. 6. After upgrade, verify the new version is installed and SIP ALG functionality is restored if needed using 'set security alg sip enable' (enabled by default in later versions)
  7. 7. Confirm the device is functioning normally post-upgrade
Caveat Standard Junos upgrade precautions apply; test in lab environment before production deployment

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

Fix this in Junos Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,640
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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-2026-57026 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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