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JunosOperating system · Juniper

CVE-2022-22157

CRITICAL · 9.3 CVSS v3.1 Published 2022-01-19
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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
A traffic classification vulnerability in Juniper Networks Junos OS on the SRX Series Services Gateways may allow an attacker to bypass Juniper Deep Packet Inspection (JDPI) rules and access unauthorized networks or resources, when 'no-syn-check' is enabled on the device. JDPI incorrectly classifies out-of-state asymmetric TCP flows as the dynamic-application INCONCLUSIVE instead of UNKNOWN, which is more permissive, causing the firewall to allow traffic to be forwarded that should have been denied. This issue only occurs when 'set security flow tcp-session no-syn-check' is configured on the device. This issue affects Juniper Networks Junos OS on SRX Series: 18.4 versions prior to 18.4R2-S9, 18.4R3-S9; 19.1 versions prior to 19.1R2-S3, 19.1R3-S6; 19.2 versions prior to 19.2R1-S7, 19.2R3-S3; 19.3 versions prior to 19.3R2-S6, 19.3R3-S2; 19.4 versions prior to 19.4R2-S5, 19.4R3-S3; 20.1 versions prior to 20.1R2-S2, 20.1R3; 20.2 versions prior to 20.2R3-S1; 20.3 versions prior to 20.3R3; 20.4 versions prior to 20.4R2-S1, 20.4R3; 21.1 versions prior to 21.1R1-S1, 21.1R2. This issue does not affect Juniper Networks Junos OS versions prior to 18.4R1.

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 traffic classification bypass vulnerability in Juniper Networks Junos OS on SRX Series allows attackers to circumvent Juniper Deep Packet Inspection (JDPI) rules. When 'no-syn-check' is configured, JDPI incorrectly classifies out-of-state asymmetric TCP flows as 'INCONCLUSIVE' instead of 'UNKNOWN', which is more permissive and causes the firewall to forward traffic that should be denied.

MitigationUpgrade to a fixed Junos OS version per the vendor advisory; if the 'no-syn-check' feature is not required, disabling 'set security flow tcp-session no-syn-check' eliminates the attack vector.

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:= 18.4= 19.1= 19.2= 19.3= 19.4= 20.1= 20.2= 20.3= 20.4= 21.1= 21.2

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
Changed
Confidentiality
High
Integrity
Low
Availability
None

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

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 and Junos OS version
    Run 'show version' or 'show chassis hardware' on the device to confirm it is an SRX Series device and record the exact Junos OS version number.
    Affected if The device is SRX Series and runs Junos version 18.4, 19.1, 19.2, 19.3, 19.4, 20.1, 20.2, 20.3, 20.4, 21.1, or 21.2
  2. Check if no-syn-check is enabled
    Run 'show configuration security flow tcp-session' or view the active configuration with 'show configuration | display set | match no-syn-check' to see if the 'no-syn-check' option is configured.
    Affected if The output shows 'set security flow tcp-session no-syn-check' or similar configuration enabling this feature
  3. Confirm JDPI inspection is in use
    Run 'show configuration security idp' or 'show configuration security policies' to check if Juniper Deep Packet Inspection (IDP/JDPI) policies are defined for traffic enforcement.
    Affected if IDP/JDPI policies or rules are configured on the device

The environment is affected if it is an SRX Series device running one of the listed affected Junos versions with the 'no-syn-check' feature enabled and JDPI/IDP policies configured for traffic inspection.

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

Upgrade to a fixed Junos OS version per the vendor advisory; if the 'no-syn-check' feature is not required, disabling 'set security flow tcp-session no-syn-check' eliminates the attack vector.

Recommended fix High confidence

Upgrade to Junos OS 18.4R2-S9/18.4R3-S9, 19.1R2-S3/19.1R3-S6, 19.2R1-S7/19.2R3-S3, or 19.3R2-S6/19.3R3-S2 (or later stable releases)

  1. 1. Identify the current Junos OS version on the SRX Series device using 'show version'
  2. 2. Identify if 'no-syn-check' is enabled by running 'show configuration security flow tcp-session'
  3. 3. If 'no-syn-check' is configured, assess whether it is still required for the network design
  4. 4. If possible, remove the 'no-syn-check' configuration with 'delete security flow tcp-session no-syn-check' and commit the change
  5. 5. If 'no-syn-check' is required, plan for a Junos OS upgrade to a fixed version
  6. 6. Before upgrading, back up the current configuration using 'request system configuration rescue save'
  7. 7. Upgrade to one of the fixed versions: 18.4R2-S9, 18.4R3-S9, 19.1R2-S3, 19.1R3-S6, 19.2R1-S7, 19.2R3-S3, 19.3R2-S6, or 19.3R3-S2 (or later)
  8. 8. After upgrade, verify JDPI classification is working correctly for asymmetric TCP flows
Caveat Upgrading Junos OS may cause temporary service disruption; ensure maintenance window and test in lab first; some configuration changes may be needed for compatibility with newer versions

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

Fix this in Junos Scoped from the published advisory
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,120
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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-2022-22157 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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