dbcve.org
JunosOperating system · Juniper

CVE-2020-1655

MEDIUM · 5.3 CVSS v3.1 Published 2020-07-17
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
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
When a device running Juniper Networks Junos OS with MPC7, MPC8, or MPC9 line cards installed and the system is configured for inline IP reassembly, used by L2TP, MAP-E, GRE, and IPIP, the packet forwarding engine (PFE) will become disabled upon receipt of large packets requiring fragmentation, generating the following error messages: [LOG: Err] MQSS(0): WO: Packet Error - Error Packets 1, Connection 29 [LOG: Err] eachip_hmcif_rx_intr_handler(7259): EA[0:0]: HMCIF Rx: Injected checksum error detected on WO response - Chunk Address 0x0 [LOG: Err] MQSS(0): DRD: RORD1: CMD reorder ID error - Command 11, Reorder ID 1838, QID 0 [LOG: Err] MQSS(0): DRD: UNROLL0: HMC chunk length error in stage 5 - Chunk Address: 0x4321f3 [LOG: Err] MQSS(0): DRD: UNROLL0: HMC chunk address error in stage 5 - Chunk Address: 0x0 [LOG: Notice] Error: /fpc/8/pfe/0/cm/0/MQSS(0)/0/MQSS_CMERROR_DRD_RORD_ENG_INT_REG_CMD_FSM_STATE_ERR (0x2203cc), scope: pfe, category: functional, severity: major, module: MQSS(0), type: DRD_RORD_ENG_INT: CMD FSM State Error [LOG: Notice] Performing action cmalarm for error /fpc/8/pfe/0/cm/0/MQSS(0)/0/MQSS_CMERROR_DRD_RORD_ENG_INT_REG_CMD_FSM_STATE_ERR (0x2203cc) in module: MQSS(0) with scope: pfe category: functional level: major [LOG: Notice] Performing action get-state for error /fpc/8/pfe/0/cm/0/MQSS(0)/0/MQSS_CMERROR_DRD_RORD_ENG_INT_REG_CMD_FSM_STATE_ERR (0x2203cc) in module: MQSS(0) with scope: pfe category: functional level: major [LOG: Notice] Performing action disable-pfe for error /fpc/8/pfe/0/cm/0/MQSS(0)/0/MQSS_CMERROR_DRD_RORD_ENG_INT_REG_CMD_FSM_STATE_ERR (0x2203cc) in module: MQSS(0) with scope: pfe category: functional level: major By continuously sending fragmented packets that cannot be reassembled, an attacker can repeatedly disable the PFE causing a sustained Denial of Service (DoS). This issue affects Juniper Networks Junos OS: 17.2 versions prior to 17.2R3-S4 on MX Series; 17.3 versions prior to 17.3R3-S8 on MX Series; 17.4 versions prior to 17.4R2-S10, 17.4R3-S2 on MX Series; 18.1 versions prior to 18.1R3-S10 on MX Series; 18.2 versions prior to 18.2R3-S3 on MX Series; 18.2X75 versions prior to 18.2X75-D41, 18.2X75-D430, 18.2X75-D65 on MX Series; 18.3 versions prior to 18.3R1-S7, 18.3R2-S4, 18.3R3-S1 on MX Series; 18.4 versions prior to 18.4R1-S7, 18.4R2-S4, 18.4R3 on MX Series; 19.1 versions prior to 19.1R1-S5, 19.1R2-S1, 19.1R3 on MX Series; 19.2 versions prior to 19.2R1-S4, 19.2R2 on MX Series; 19.3 versions prior to 19.3R2-S2, 19.3R3 on MX Series. This issue is specific to inline IP reassembly, introduced in Junos OS 17.2. Versions of Junos OS prior to 17.2 are unaffected by this vulnerability.

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

On Juniper MX Series devices with MPC7, MPC8, or MPC9 line cards running Junos OS 17.2 or later with inline IP reassembly enabled (used by L2TP, MAP-E, GRE, and IPIP), specially crafted large fragmented packets trigger a PFE error causing the Packet Forwarding Engine to disable. Repeatedly sending un-reassemblable fragments allows an attacker to cause sustained DoS by repeatedly crashing the PFE.

MitigationUpgrade Junos OS to the specified patched versions for each branch (17.2R3-S4, 17.3R3-S8, 17.4R2-S10/17.4R3-S2, 18.1R3-S10, 18.2R3-S3, 18.2X75-D41/D430/D65, 18.3R1-S7/18.3R2-S4/18.3R3-S1, 18.4R1-S7/18.4R2-S4/18.4R3, 19.1R1-S5/19.1R2-S1/19.1R3, 19.2R1-S4/19.2R2, 19.3R2-S2/19.3R3). If upgrading is not immediately possible, consider disabling inline IP reassembly if not required.

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:= 17.2= 17.3= 17.4= 18.1= 18.2= 18.2x75= 18.3= 18.4= 19.1= 19.2= 19.3

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
Low

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

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 MX Series hardware
    Run 'show chassis hardware' and look for MPC7, MPC8, or MPC9 line cards in the output
    Affected if The device is an MX Series with MPC7, MPC8, or MPC9 line cards present
  2. Check Junos OS version
    Run 'show version' and compare the installed version against the affected list: 17.2, 17.3, 17.4, 18.1, 18.2, 18.2x75, 18.3, 18.4, 19.1, 19.2, 19.3
    Affected if The installed Junos OS version matches one of the listed affected versions
  3. Verify inline IP reassembly status
    Run 'show configuration | display set | match reassembly' or check the configuration under 'set chassis fpc' for inline-reassembly settings
    Affected if Inline IP reassembly is enabled in the configuration
  4. Check for affected services
    Run 'show configuration | display set | match "l2tp|map-e|gre|ipip"' to see if any of L2TP, MAP-E, GRE, or IPIP tunnels are configured
    Affected if Any of these features are configured and active on the device

You are affected if you have an MX Series with MPC7/8/9 line cards, run an affected Junos version, and have both inline IP reassembly enabled AND one or more of L2TP, MAP-E, GRE, or IPIP configured.

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 the specified patched versions for each branch (17.2R3-S4, 17.3R3-S8, 17.4R2-S10/17.4R3-S2, 18.1R3-S10, 18.2R3-S3, 18.2X75-D41/D430/D65, 18.3R1-S7/18.3R2-S4/18.3R3-S1, 18.4R1-S7/18.4R2-S4/18.4R3, 19.1R1-S5/19.1R2-S1/19.1R3, 19.2R1-S4/19.2R2, 19.3R2-S2/19.3R3). If upgrading is not immediately possible, consider disabling inline IP reassembly if not required.

Fix this in Junos Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2020-1655 — 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-2020-1655 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