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JunosOperating system · Juniper

CVE-2020-1603

HIGH · 8.6 CVSS v3.1 Published 2020-01-15
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
95/100
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
Specific IPv6 packets sent by clients processed by the Routing Engine (RE) are improperly handled. These IPv6 packets are designed to be blocked by the RE from egressing the RE. Instead, the RE allows these specific IPv6 packets to egress the RE, at which point a mbuf memory leak occurs within the Juniper Networks Junos OS device. This memory leak eventually leads to a kernel crash (vmcore), or the device hanging and requiring a power cycle to restore service, creating a Denial of Service (DoS) condition. During the time where mbufs are rising, yet not fully filled, some traffic from client devices may begin to be black holed. To be black holed, this traffic must match the condition where this traffic must be processed by the RE. Continued receipt and attempted egress of these specific IPv6 packets from the Routing Engine (RE) will create an extended Denial of Service (DoS) condition. Scenarios which have been observed are: 1. In a single chassis, single RE scenario, the device will hang without vmcore, or a vmcore may occur and then hang. In this scenario the device needs to be power cycled. 2. In a single chassis, dual RE scenario, the device master RE will fail over to the backup RE. In this scenario, the master and the backup REs need to be reset from time to time when they vmcore. There is no need to power cycle the device. 3. In a dual chassis, single RE scenario, the device will hang without vmcore, or a vmcore may occur and then hang. In this scenario, the two chassis' design relies upon some type of network level redundancy - VRRP, GRES, NSR, etc. - 3.a In a commanded switchover, where nonstop active routing (NSR) is enabled no session loss is observed. 4. In a dual chassis, dual chassis scenario, rely upon the RE to RE failover as stated in the second scenario. In the unlikely event that the device does not switch RE to RE gracefully, then the fallback position is to the network level services scenario in the third scenario. This issue affects: Juniper Networks Junos OS 16.1 versions prior to 16.1R7-S6; 16.1 version 16.1X70-D10 and later; 16.2 versions prior to 16.2R2-S11; 17.1 versions prior to 17.1R2-S11, 17.1R3-S1; 17.2 versions prior to 17.2R1-S9, 17.2R2-S8, 17.2R3-S3; 17.3 versions prior to 17.3R3-S6; 17.4 versions prior to 17.4R2-S9, 17.4R3; 18.1 versions prior to 18.1R3-S7; 18.2 versions prior to 18.2R3-S2; 18.2X75 versions prior to 18.2X75-D50, 18.2X75-D410; 18.3 versions prior to 18.3R1-S6, 18.3R2-S2, 18.3R3; 18.4 versions prior to 18.4R1-S6, 18.4R2-S2, 18.4R3; 19.1 versions prior to 19.1R1-S3, 19.1R2; 19.2 versions prior to 19.2R1-S2, 19.2R2. This issue does not affect releases prior to Junos OS 16.1R1.

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 memory leak vulnerability exists in the Routing Engine of Juniper Junos OS where specific IPv6 packets improperly handled by the RE are allowed to egress when they should be blocked. This causes an mbuf memory leak that eventually leads to kernel crashes (vmcore) or device hang requiring power cycle, creating a DoS condition. During the leak, some client traffic may also be black holed.

MitigationUpgrade Junos OS to a fixed version (16.1R7-S6, 16.1X70-D10+, 17.1R2-S11+, 17.2R3-S3+, 17.3R3-S6+, 17.4R2-S9+, 18.1R3-S7+, 18.2R3-S2+, 18.2X75-D50+, 18.3R3+, 18.4R3+, 19.1R2+, or 19.2R2+). Consider network-level redundancy and filtering IPv6 traffic from untrusted sources as a temporary workaround.

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:= 16.1= 16.1x70= 16.2= 17.1= 17.2= 17.3= 17.4= 18.1= 18.2= 18.2x75= 18.3= 18.4

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
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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 the Junos OS version
    Run 'show version' on the device CLI to obtain the installed version number
    Affected if The installed version matches one of the affected releases: 16.1, 16.1x70, 16.2, 17.1, 17.2, 17.3, 17.4, 18.1, 18.2, 18.2x75, 18.3, or 18.4 (any variant within these major.minor branches)
  2. Verify IPv6 is configured
    Run 'show ipv6 interface' or inspect the configuration with 'show configuration | match ipv6' to determine if IPv6 is enabled on any interface
    Affected if IPv6 is actively configured on any interface - the vulnerability is triggered by specific IPv6 packets being processed by the Routing Engine
  3. Check for kernel crash indicators
    Run 'show system core-dumps' or look in /var/crash/ for vmcore files, and review recent system logs for unexpected kernel panics or reboots
    Affected if Recent vmcore files exist or kernel crash events are logged, especially if accompanied by symptoms of memory exhaustion
  4. Assess device stability and uptime
    Run 'show system uptime' to check for unexpected reboots, and monitor for recent spontaneous reboots or hang conditions requiring power cycle
    Affected if The device has experienced unexplained crashes or required power cycling, which could indicate the mbuf memory leak has caused kernel instability

A device is likely affected if it runs a vulnerable Junos version listed in the affected releases, has IPv6 configured, and shows signs of memory-related crashes or instability consistent with the mbuf leak described in the CVE.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Junos OS to a fixed version (16.1R7-S6, 16.1X70-D10+, 17.1R2-S11+, 17.2R3-S3+, 17.3R3-S6+, 17.4R2-S9+, 18.1R3-S7+, 18.2R3-S2+, 18.2X75-D50+, 18.3R3+, 18.4R3+, 19.1R2+, or 19.2R2+). Consider network-level redundancy and filtering IPv6 traffic from untrusted sources as a temporary workaround.

Fix this in Junos Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,840
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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-2020-1603 in production — separate from our analysis above.

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What belongs here
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