CVE-2021-0277

Sustained l2cpd crashes via malformed LLDP frames

Published Jul 15, 2021 · Updated Sep 16, 2024

Out-of-bounds reads in Juniper Networks Junos OS and Junos OS Evolved allow remote attackers to crash l2cpd or execute code. The daemon reads beyond a buffer while processing specially crafted LLDP frames received from the local broadcast domain. Continued frame delivery repeatedly crashes l2cpd and sustains service interruption; Juniper reports code execution as an additional, unconfirmed impact.

CVSS severity8.8
High
EPSS probability0.65%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds reads in Juniper Networks Junos OS and Junos OS Evolved allow remote attackers to crash l2cpd or execute code. The daemon reads beyond a buffer while processing specially crafted LLDP frames received from the local broadcast domain. Continued frame delivery repeatedly crashes l2cpd and sustains service interruption; Juniper reports code execution as an additional, unconfirmed impact.

The record

CVE
CVE-2021-0277
Published
Jul 15, 2021
Updated
Sep 16, 2024
Vendor
Juniper Networks
Product
Junos OS Evolved
Classifications
CWE-125, T1499
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <20.4R2-EVO

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OS Evolvedversion=unspecified <20.4R2-EVO
Juniper Networks · Junos OSversion=12.3 <12.3R12-S18; version=15.1 <15.1R7-S9; version=17.3 <17.3R3-S12; version=17.4 <17.4R2-S13, 17.4R3-S5; version=18.1 <18.1R3-S13; version=18.2 <18.2R3-S8; version=18.3 <18.3R3-S5; version=18.4 <18.4R2-S8, 18.4R3-S8; version=19.1 <19.1R3-S5; version=19.2 <19.2R3-S3; version=19.3 <19.3R2-S6, 19.3R3-S2; version=19.4 <19.4R1-S4, 19.4R2-S4, 19.4R3-S3; version=20.1 <20.1R2-S2, 20.1R3; version=20.2 <20.2R3-S1; version=20.3 <20.3R2-S1, 20.3R3; version=20.4 <20.4R2

Published CVSS scores

5.8NIST NVDAV:A/AC:L/Au:N/C:P/I:P/A:P
8.8Juniper Networks, Inc.CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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