What is CVE-2021-0224?

CVE-2021-0224 is a medium-severity vulnerability in Juniper Junos, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 6.5/10. Published 2021-04-22.

How severe is CVE-2021-0224?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Resource exhaustion in Juniper Junos

CVE-2021-0224

A vulnerability in the handling of internal resources necessary to bring up a large number of Layer 2 broadband remote access subscriber (BRAS) nodes in Juniper Networks Junos OS can cause the Access Node Control Protocol daemon (ANCPD) to crash and restart, leading to a Denial of Service (DoS) condition. Continued processing of spoofed subscriber nodes will create a sustained Denial of Service (DoS) condition. When the number of subscribers attempting to connect exceeds the configured maximum-discovery-table-entries value, the subscriber fails to map to an internal neighbor entry, causing the ANCPD process to crash. This issue affects Juniper Networks Junos OS: All versions prior to 17.3R3-S12; 17.4 versions prior to 17.4R2-S13; 18.1 versions prior to 18.1R3-S13; 18.2 versions prior to 18.2R3-S8; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R1-S8, 18.4R3-S8; 19.1 versions prior to 19.1R3-S4; 19.2 versions prior to 19.2R3-S2; 19.3 versions prior to 19.3R3-S1; 19.4 versions prior to 19.4R3-S1; 20.1 versions prior to 20.1R2; 20.2 versions prior to 20.2R2; 20.3 versions prior to 20.3R2.

Published 2021-04-22 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.004 (29.7th percentile), scored 2026-10-03.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 30th percentile — 29.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000

Affected products

Juniper Junos — versions 17.3, 17.4, 18.1
Juniper Networks Junos OS — versions All, 17.4, 18.1

Weakness classification (CWE)

CWE-770 — Allocation of Resources Without Limits or Throttling

References

kb.juniper.net/JSA11119 (Vendor Advisory)

Frequently asked questions

What is CVE-2021-0224?: CVE-2021-0224 is a medium-severity vulnerability in Juniper Junos, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 6.5/10. Published 2021-04-22.
How severe is CVE-2021-0224?: Medium severity. CVSS v3 base score is 6.5 out of 10.