CVE intelligence and bounded remediation

CVE-2021-0238 — Juniper Junos security vulnerability

Medium CVSS 5.5

When a MX Series is configured as a Broadband Network Gateway (BNG) based on Layer 2 Tunneling Protocol (L2TP), executing certain CLI command may cause the system to run out of disk space, excessive disk usage may cause other complications. An administrator can use the following CLI command to monitor the available disk space: user@device> show system storage Filesystem Size Used Avail Capacity Mounted on /dev/gpt/junos 19G 18G 147M 99% /.mount <<<<< running out of space tmpfs 21G 16K 21G 0% /.mount/tmp tmpfs 5.3G 1.7M 5.3G 0% /.mount/mfs This issue affects Juniper Networks Junos OS on MX Series: 17.3R1 and later versions prior to 17.4R3-S5, 18.1 versions prior to 18.1R3-S13, 18.2 versions prior to 18.2R3-S7; 18.3 versions prior to 18.3R3-S4; 18.4 versions prior to 18.4R3-S7; 19.1 versions prior to 19.1R3-S4; 19.2 versions prior to 19.2R1-S6, 19.2R3-S2; 19.3 versions prior to 19.3R3-S2; 19.4 versions prior to 19.4R2-S4, 19.4R3-S2; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R2-S3, 20.2R3; 20.3 versions prior to 20.3R2; 20.4 versions prior to 20.4R1-S1, 20.4R2; This issue does not affect Juniper Networks Junos OS versions prior to 17.3R1.

Severity
Medium
CVSS
5.5 (3.1)
Published
2021-04-22
CISA KEV
Not currently listed
Ecosystem
operating-system
Weaknesses
CWE-400

Affected products

  • juniper / junos / 17.3

Showing 1 representative product identities from 133 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.

Matched remediation archetype

Resource exhaustion and denial of service

This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.

Check exposure

  • Identify attacker-influenced work factors including input size, nesting, compression, fan-out, regex cost, allocation, recursion, retries, and connection lifetime.
  • Map per-request and shared CPU, memory, disk, descriptor, thread, queue, and downstream-service limits.
  • Determine whether authentication, tenancy, quotas, and rate controls apply before expensive processing begins.

Remediate safely

  • Bound input size, nesting, expansion, work, concurrency, queue depth, retries, and execution time before resource-intensive processing.
  • Release resources on every success, error, cancellation, and timeout path and use backpressure instead of unbounded buffering.
  • Update affected components and add small deterministic tests that assert resource ceilings rather than exhausting a host.

Authoritative sources

Complete CVE record and remediation plan

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