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   JSA11216 - 2021-10 Security Bulletin: Junos OS: MX Series: Receipt of
 specific packet on MS-MPC/MS-MIC causes line card reset (CVE-2021-31351)
                              15 October 2021


        AusCERT Security Bulletin Summary

Product:           Junos OS
Publisher:         Juniper Networks
Operating System:  Juniper
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2021-31351  

Original Bulletin: 

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2021-10 Security Bulletin: Junos OS: MX Series: Receipt of specific packet on MS-MPC/MS-MIC causes line card reset (CVE-2021-31351)

Article ID  : JSA11216
Last Updated: 14 Oct 2021
Version     : 2.0

Product Affected:
This issue affects specific versions of Junos OS (see below). Affected
platforms: MX Series.

An Improper Check for Unusual or Exceptional Conditions in packet processing on
the MS-MPC/MS-MIC utilized by Juniper Networks Junos OS allows a malicious
attacker to send a specific packet, triggering the MS-MPC/MS-MIC to reset,
causing a Denial of Service (DoS).

Continued receipt and processing of this packet will create a sustained Denial
of Service (DoS) condition.

This issue only affects specific versions of Juniper Networks Junos OS on MX

  o 17.3R3-S11;
  o 17.4R2-S13;
  o 17.4R3 prior to 17.4R3-S5;
  o 18.1R3-S12;
  o 18.2R2-S8, 18.2R3-S7, 18.2R3-S8;
  o 18.3R3-S4;
  o 18.4R3-S7;
  o 19.1R3-S4, 19.1R3-S5;
  o 19.2R1-S6;
  o 19.3R3-S2;
  o 19.4R2-S4, 19.4R2-S5;
  o 19.4R3-S2;
  o 20.1R2-S1;
  o 20.2R2-S2, 20.2R2-S3, 20.2R3;
  o 20.3R2, 20.3R2-S1;
  o 20.4R1, 20.4R1-S1, 20.4R2;
  o 21.1R1;

This issue does not affect any version of Juniper Networks Junos OS prior to

Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

This issue was seen during production usage.

This issue has been assigned CVE-2021-31351 .


The following software releases have been updated to resolve this specific
issue: Junos OS 17.3R3-S12, 17.4R3-S5, 18.1R3-S13, 18.3R3-S5, 18.4R3-S8,
19.1R3-S6, 19.2R1-S7, 19.2R3-S2, 19.3R2-S6, 19.3R3-S3, 19.4R3-S3, 20.1R2-S2,
20.1R3, 20.2R3-S1, 20.3R3, 20.4R2-S1, 20.4R3, 21.1R1-S1, 21.1R2, 21.2R1, and
all subsequent releases.

Note: Only those releases listed in the PROBLEM section above are affected.
This fix has also been proactively committed into other releases that are not
vulnerable to this issue.

This issue is being tracked as 1577814 .

There are no viable workarounds for this issue.
Software releases or updates are available for download at https://
Modification History:

2021-10-13: Initial Publication.
2021-10-14: Typo in affected releases (20.2R3-S3 -> 20.2R2-S3)

CVSS Score:
7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
Severity Level:
Severity Assessment:
Information for how Juniper Networks uses CVSS can be found at KB 16446 "Common
Vulnerability Scoring System (CVSS) and Juniper's Security Advisories."

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