Junos OS: MX Series: Traffic drops will be observed if MS-MPC/MS-PIC resources are consumed by certain traffic causing a partial DoS

Description

On MX Series platforms with MS-MPC/MS-MIC, an Allocation of Resources Without Limits or Throttling vulnerability in Juniper Networks Junos OS allows an unauthenticated network attacker to cause a partial Denial of Service (DoS) with a high rate of specific traffic. If a Class of Service (CoS) rule is attached to the service-set and a high rate of specific traffic is processed by this service-set, for some of the other traffic which has services applied and is being processed by this MS-MPC/MS-MIC drops will be observed. Continued receipted of this high rate of specific traffic will create a sustained Denial of Service (DoS) condition. This issue affects: Juniper Networks Junos OS on MX Series with MS-MPC/MS-MIC: All versions prior to 17.4R3-S5; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R3-S9; 19.1 versions prior to 19.1R3-S6; 19.2 versions prior to 19.2R1-S7, 19.2R3-S3; 19.3 versions prior to 19.3R2-S7, 19.3R3-S3; 19.4 versions prior to 19.4R3-S5; 20.1 versions prior to 20.1R2-S2, 20.1R3-S1; 20.2 versions prior to 20.2R3-S2; 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.

Scores

EPSS (exploitation in 30 days)

0.97% · top 38% of all CVEs (6 Nov 2026)

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.3.

Weakness

• CWE-770 Allocation of Resources Without Limits or Throttling (opens in a new tab)All about CWE-770 and its CVEs
• Denial of Service (DoS)

Affected products

• Juniper Networks · Junos OS

  • affected unspecified – < 17.4R3-S5
  • affected 18.3 – < 18.3R3-S5
  • affected 18.4 – < 18.4R3-S9
  • affected 19.1 – < 19.1R3-S6
  • affected 19.2 – < 19.2R1-S7, 19.2R3-S3
  • affected 19.3 – < 19.3R2-S7, 19.3R3-S3
  • affected 19.4 – < 19.4R3-S5
  • affected 20.1 – < 20.1R2-S2, 20.1R3-S1
  • affected 20.2 – < 20.2R3-S2
  • affected 20.3 – < 20.3R3
  • affected 20.4 – < 20.4R2-S1, 20.4R3
  • affected 21.1 – < 21.1R1-S1, 21.1R2

What to do

Solution: The following software releases have been updated to resolve this specific issue: 17.4R3-S5, 18.3R3-S5, 18.4R3-S9, 19.1R3-S6, 19.2R1-S7, 19.2R3-S3, 19.3R2-S7, 19.3R3-S3, 19.4R3-S5, 20.1R2-S2, 20.1R3-S1, 20.2R3-S2, 20.3R3, 20.4R2-S1, 20.4R3, 21.1R1-S1, 21.1R2, 21.2R1, and all subsequent releases.

Workaround: There are no viable workarounds for this issue.

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

References (1)

• https://kb.juniper.net/JSA11231 (opens in a new tab)x_refsource_CONFIRMx_transferred

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2021-31369](https://trackcve.app/badge/CVE-2021-31369.svg)](https://trackcve.app/cve/CVE-2021-31369)

Record last updated 16 Sept 2024, 18:34 UTC.