CVE intelligence and bounded remediation

CVE-2021-0273 — Juniper Junos security vulnerability

Medium CVSS 5.3

An always-incorrect control flow implementation in the implicit filter terms of Juniper Networks Junos OS and Junos OS Evolved on ACX5800, EX9200 Series, MX10000 Series, MX240, MX480, MX960 devices with affected Trio line cards allows an attacker to exploit an interdependency in the PFE UCODE microcode of the Trio chipset with various line cards to cause packets destined to the devices interfaces to cause a Denial of Service (DoS) condition by looping the packet with an unreachable exit condition ('Infinite Loop'). To break this loop once it begins one side of the affected LT interfaces will need to be disabled. Once disabled, the condition will clear and the disabled LT interface can be reenabled. Continued receipt and processing of these packets will create a sustained Denial of Service (DoS) condition. This issue only affects LT-LT interfaces. Any other interfaces are not affected by this issue. This issue affects the following cards: MPCE Type 3 3D MPC4E 3D 32XGE MPC4E 3D 2CGE+8XGE EX9200 32x10G SFP EX9200-2C-8XS FPC Type 5-3D FPC Type 5-LSR EX9200 4x40G QSFP An Indicator of Compromise (IoC) can be seen by examining the traffic of the LT-LT interfaces for excessive traffic usi…

Severity
Medium
CVSS
5.3 (3.1)
Published
2021-04-22
CISA KEV
Not currently listed
Ecosystem
operating-system
Weaknesses
CWE-670, CWE-835

Affected products

  • juniper / junos / 15.1

Showing 1 representative product identities from 226 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.

Matched remediation archetype

Resource exhaustion and denial of service

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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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