CVE-2021-0254

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2022-05-24. NVD baseline CVSS 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
9.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 3%CVSS: 9.8Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

A buffer size validation vulnerability in the overlayd service of Juniper Networks Junos OS may allow an unauthenticated remote attacker to send specially crafted packets to the device, triggering a partial Denial of Service (DoS) condition, or leading to remote code execution (RCE). Continued receipt and processing of these packets will sustain the partial DoS. The overlayd daemon handles Overlay OAM packets, such as ping and traceroute, sent to the overlay. The service runs as root by default and listens for UDP connections on port 4789. This issue results from improper buffer size validation, which can lead to a buffer overflow. Unauthenticated attackers can send specially crafted packets to trigger this vulnerability, resulting in possible remote code execution. overlayd runs by default in MX Series, ACX Series, and QFX Series platforms. The SRX Series does not support VXLAN and is therefore not vulnerable to this issue. Other platforms are also vulnerable if a Virtual Extensible LAN (VXLAN) overlay network is configured. This issue affects Juniper Networks Junos OS: 15.1 versions prior to 15.1R7-S9; 17.3 versions prior to 17.3R3-S11; 17.4 versions prior to 17.4R2-S13, 17.4R3-S4; 18.1 versions prior to 18.1R3-S12; 18.2 versions prior to 18.2R2-S8, 18.2R3-S7; 18.3 versions prior to 18.3R3-S4; 18.4 versions prior to 18.4R1-S8, 18.4R2-S7, 18.4R3-S7; 19.1 versions prior to 19.1R2-S2, 19.1R3-S4; 19.2 versions prior to 19.2R1-S6, 19.2R3-S2; 19.3 versions prior to 19.3R3-S1; 19.4 versions prior to 19.4R2-S4, 19.4R3-S1; 20.1 versions prior to 20.1R2-S1, 20.1R3; 20.2 versions prior to 20.2R2, 20.2R2-S1, 20.2R3; 20.3 versions prior to 20.3R1-S1.

CVSS v3
9.8
EG Score
9.8(medium)
EPSS
83.4%
KEV
Not listed

Published

April 22, 2021

Last Modified

November 21, 2024

Advisory Details (1)

Auto-updated Jul 5, 2026
No patch confirmed yet.
generic

CEC Juniper Community

https://kb.juniper.net/JSA11147

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 12× in last 7d / 46× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-16 17:00 UTCEPSS rescore
  2. 2026-07-15 16:55 UTCEPSS rescore
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  1. 2026-06-30 23:20 UTCEPSS rescore
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  8. 2026-06-25 13:48 UTCEPSS rescore
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  23. 2026-06-15 17:46 UTCEPSS rescore
  24. 2026-06-14 23:15 UTCEPSS rescore
  25. 2026-06-13 22:58 UTCEPSS rescore
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  45. 2026-06-02 20:11 UTCEPSS rescore
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  50. 2026-05-31 00:15 UTCEPSS rescore
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  52. 2026-05-29 13:42 UTCEPSS rescore
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  55. 2026-05-27 13:39 UTCEPSS rescore
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  57. 2026-05-26 17:57 UTCEG score recompute
  58. 2026-05-26 17:57 UTCGHSA enrichment
  59. 2026-05-26 13:42 UTCEPSS rescore
  60. 2026-05-26 13:42 UTCEPSS rescore
  61. 2026-05-26 07:17 UTCEPSS rescore
  62. 2026-05-26 07:17 UTCEPSS rescore

Frequently asked(5)

What is CVE-2021-0254?
CVE-2021-0254 is a critical vulnerability published on April 22, 2021. A buffer size validation vulnerability in the overlayd service of Juniper Networks Junos OS may allow an unauthenticated remote attacker to send specially crafted packets to the device, triggering a partial Denial of Service (DoS) condition, or leading to remote code execution (RCE). Continued…
When was CVE-2021-0254 disclosed?
CVE-2021-0254 was first published in the National Vulnerability Database on April 22, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-0254 actively exploited?
CVE-2021-0254 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 83.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-0254?
CVE-2021-0254 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2021-0254?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-0254, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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