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Fencer Vulns
high 8.8

CVE-2021-0277 json

Junos OS and Junos OS Evolved: LLDP Out-of-Bounds Read vulnerability in l2cpd

published 2021-07-15 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-2896

cvss
8.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 51%
public exploits
0
none known

Summary

An Out-of-bounds Read vulnerability in the processing of specially crafted LLDP frames by the Layer 2 Control Protocol Daemon (l2cpd) of Juniper Networks Junos OS and Junos OS Evolved may allow an attacker to cause a Denial of Service (DoS), or may lead to remote code execution (RCE). Continued receipt and processing of these frames, sent from the local broadcast domain, will repeatedly crash the l2cpd process and sustain the Denial of Service (DoS) condition. This issue affects: Juniper Networks Junos OS: 12.3 versions prior to 12.3R12-S18; 15.1 versions prior to 15.1R7-S9; 17.3 versions prior to 17.3R3-S12; 17.4 versions prior to 17.4R2-S13, 17.4R3-S5; 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 18.4R2-S8, 18.4R3-S8; 19.1 versions prior to 19.1R3-S5; 19.2 versions prior to 19.2R3-S3; 19.3 versions prior to 19.3R2-S6, 19.3R3-S2; 19.4 versions prior to 19.4R1-S4, 19.4R2-S4, 19.4R3-S3; 20.1 versions prior to 20.1R2-S2, 20.1R3; 20.2 versions prior to 20.2R3-S1; 20.3 versions prior to 20.3R2-S1, 20.3R3; 20.4 versions prior to 20.4R2. Juniper Networks Junos OS Evolved versions prior to 20.4R2-EVO.

Patch / fix

  • Juniper Networks Junos OS 12.3R12-S18, 15.1R7-S9, 17.3R3-S12, 17.4R2-S13, 17.4R3-S5, 18.1R3-S13, 18.2R3-S8, 18.3R3-S5, 18.4R2-S8, 18.4R3-S8, 19.1R3-S5, 19.2R3-S3, 19.3R2-S6, 19.3R3-S2, 19.4R1-S4, 19.4R2-S4, 19.4R3-S3, 20.1R2-S2, 20.1R3, 20.2R3-S1, 20.3R2-S1, 20.3R3, 20.4R2
  • Juniper Networks Junos OS Evolved 20.4R2-EVO

Exploit prediction

0.65% chance of exploitation in the next 30 days, higher than 51% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.8 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 5.8 AV:A/AC:L/Au:N/C:P/I:P/A:P

Affected products

  • Juniper Networks Junos OS
  • Juniper Networks Junos OS Evolved

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.