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JunosOperating system · Juniper

CVE-2023-28961

MEDIUM · 5.3 CVSS v3.1 Published 2023-04-17
Fix available
A fix is available. Upgrade to 20.2 or later.
See remediation →
62/100
Remediation priority · Elevated
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
An Improper Handling of Unexpected Data Type vulnerability in IPv6 firewall filter processing of Juniper Networks Junos OS on the ACX Series devices will prevent a firewall filter with the term 'from next-header ah' from being properly installed in the packet forwarding engine (PFE). There is no immediate indication of an incomplete firewall filter commit shown at the CLI, which could allow an attacker to send valid packets to or through the device that were explicitly intended to be dropped. An indication that the filter was not installed can be identified with the following logs: fpc0 ACX_DFW_CFG_FAILED: ACX Error (dfw):dnx_dfw_rule_prepare : Config failed: Unsupported Ip-protocol 51 in the filter lo0.0-inet6-i fpc0 ACX_DFW_CFG_FAILED: ACX Error (dfw):dnx_dfw_rule_prepare : Please detach the filter, remove unsupported match and re-attach fpc0 ACX_DFW_CFG_FAILED: ACX Error (dfw):dnx_dfw_process_rule : Status:104 dnx_dfw_rule_prepare failed fpc0 ACX_DFW_CFG_FAILED: ACX Error (dfw):dnx_dfw_process_filter : Status:104 dnx_dfw_process_rule failed fpc0 ACX_DFW_CFG_FAILED: ACX Error (dfw):dnx_dfw_update_filter_in_hw : Status:104 Could not process filter(lo0.0-inet6-i) for rule expansion Unsupported match, action present. fpc0 ACX_DFW_CFG_FAILED: ACX Error (dfw):dnx_dfw_create_hw_instance : Status:104 Could not program dfw(lo0.0-inet6-i) type(IFP_DFLT_INET6_Lo0_FILTER)! [104] fpc0 ACX_DFW_CFG_FAILED: ACX Error (dfw):dnx_dfw_bind_shim : [104] Could not create dfw(lo0.0-inet6-i) type(IFP_DFLT_INET6_Lo0_FILTER) fpc0 ACX_DFW_CFG_FAILED: ACX Error (dfw):dnx_dfw_update_resolve : [100] Failed to bind filter(3) to bind point fpc0 ACX_DFW_CFG_FAILED: ACX Error (dfw):dnx_dfw_change_end : dnx_dfw_update_resolve (resolve type) failed This issue affects Juniper Networks Junos OS on ACX Series: All versions prior to 20.2R3-S7; 20.4 versions prior to 20.4R3-S4; 21.1 versions prior to 21.1R3-S3; 21.2 versions prior to 21.2R3-S4; 21.3 versions prior to 21.3R3; 21.4 versions prior to 21.4R3; 22.1 versions prior to 22.1R2.

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

In Juniper Junos OS on ACX Series devices, the IPv6 firewall filter processing improperly handles the 'next-header ah' (Authentication Header - IP protocol 51) match term. When configured, the filter fails to install in the packet forwarding engine without showing an immediate CLI error, allowing packets that should be blocked to pass through. The failure is logged with specific ACX_DFW_CFG_FAILED messages indicating unsupported IP protocol 51.

MitigationUpgrade Junos OS to a fixed version per the vendor advisory. Review existing firewall filter configurations for 'next-header ah' terms and monitor logs for ACX_DFW_CFG_FAILED errors to identify affected filters.

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:< 20.2= 20.2= 20.4= 21.1= 21.2= 21.3= 21.4= 22.1

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
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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. Confirm device is an ACX Series platform
    Run 'show chassis hardware' or check the device model at login prompt or in 'show system information' output
    Affected if Device model begins with ACX (e.g., ACX5000, ACX4000, ACX2000 series)
  2. Check Junos OS version
    Run 'show version' or 'show version detail' to obtain the installed Junos version
    Affected if Version is < 20.2, or exactly 20.2, 20.4, 21.1, 21.2, 21.3, 21.4, or 22.1
  3. Identify IPv6 firewall filters with 'next-header ah' terms
    Run 'show configuration firewall family inet6' to review IPv6 filter configurations, or use 'show configuration | match "next-header ah"' to search for the vulnerable filter terms
    Affected if Any firewall filter family inet6 contains a 'next-header ah' match term
  4. Check for ACX_DFW_CFG_FAILED log errors
    Run 'show log messages | match ACX_DFW_CFG_FAILED' or 'show system messages' to search system logs for filter configuration failure messages
    Affected if Logs contain ACX_DFW_CFG_FAILED entries mentioning IP protocol 51 or 'ah'

User is affected if running Junos on ACX Series, the version is in the affected list, and an IPv6 firewall filter with 'next-header ah' is configured, with or without corresponding ACX_DFW_CFG_FAILED errors in logs indicating the filter failed to install properly.

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 20.2 or later
Fixed in 20.2
Interim mitigation

Upgrade Junos OS to a fixed version per the vendor advisory. Review existing firewall filter configurations for 'next-header ah' terms and monitor logs for ACX_DFW_CFG_FAILED errors to identify affected filters.

Recommended fix High confidence

Upgrade to 20.2R3-S7 or later, 20.4R3-S4 or later, 21.1R3-S3 or later, 21.2R3-S4 or later, 21.3R3 or later, 21.4R3 or later, or 22.1R2 or later - preferably latest stable release in your branch

  1. 1. Identify the current Junos OS version on the ACX Series device using 'show version'
  2. 2. Review firewall filter configurations for any terms using 'from next-header ah' (IP protocol 51) in IPv6 filters
  3. 3. Check system logs for ACX_DFW_CFG_FAILED errors indicating filter installation failures
  4. 4. Plan maintenance window for upgrade as this requires device reboot
  5. 5. Before upgrade, back up current configuration using 'request system configuration rescue save'
  6. 6. Download the appropriate fixed Junos OS version for the ACX Series from Juniper Networks support portal
  7. 7. Upgrade using 'request system software add <package> reboot' or through Junos Space
  8. 8. After reboot, verify the new version with 'show version'
Caveat Standard Junos upgrade precautions apply - test configuration compatibility in lab first; some legacy filter terms may need rewriting

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

Fix this in Junos Scoped from the published advisory
  • Consultation4.0 h
  • Implementation3.0 h
  • Testing4.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,300
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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-2023-28961 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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