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CVE-2023-36849Junos OS and Junos OS Evolved: The l2cpd will crash when a malformed LLDP packet is received

Description

An Improper Check or Handling of Exceptional Conditions vulnerability in the Layer-2 control protocols daemon (l2cpd) of Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated adjacent attacker to cause a Denial of Service (DoS). When a malformed LLDP packet is received, l2cpd will crash and restart. The impact of the l2cpd crash is reinitialization of STP protocols (RSTP, MSTP or VSTP), and MVRP and ERP. Also, if any services depend on LLDP state (like PoE or VoIP device recognition), then these will also be affected. Continued receipt of such packets will lead to a sustained Denial of Service. This issue affects: Juniper Networks Junos OS 21.4 versions prior to 21.4R3-S3; 22.1 versions prior to 22.1R3-S3; 22.2 versions prior to 22.2R2-S1, 22.2R3; 22.3 versions prior to 22.3R2. Juniper Networks Junos OS Evolved 21.4-EVO versions prior to 21.4R3-S2-EVO; 22.1-EVO versions prior to 22.1R3-S3-EVO; 22.2-EVO versions prior to 22.2R2-S1-EVO, 22.2R3-EVO; 22.3-EVO versions prior to 22.3R2-EVO.

Timeline

  1. ID reserved

    By juniper

  2. · 17 days later

    Published

  3. · 16 months later

    Record updated

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

CVSS scores of CVE-2023-36849, by who scored it
Scored byCVSSScoreVector
juniperCNA (assigner)3.1Medium6.5CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVDNVD · Modified3.1Medium6.5CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS (exploitation in 30 days)
0.30% · top 77% of all CVEs (12 Nov 2026)
CISA SSVC
Exploitation: none · Automatable: no · Technical impact: partial
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.5.

Affected products

  • Juniper Networks · Junos OS

    • affected 21.4 – < 21.4R3-S3
    • affected 22.1 – < 22.1R3-S3
    • affected 22.2 – < 22.2R2-S1, 22.2R3
    • affected 22.3 – < 22.3R2

  • Juniper Networks · Junos OS Evolved

    • affected 21.4 – < 21.4R3-S2-EVO
    • affected 22.1 – < 22.1R3-S3-EVO
    • affected 22.2 – < 22.2R2-S1-EVO, 22.2R3-EVO
    • affected 22.3 – < 22.3R2-EVO

What to do

Solution: The following software releases have been updated to resolve this specific issue: Junos OS: 21.4R3-S3, 22.1R3-S3, 22.2R2-S1, 22.2R3, 22.3R2, 22.4R1, and all subsequent releases. Junos OS Evolved: 21.4R3-S2-EVO, 22.1R3-S3-EVO, 22.2R2-S1-EVO, 22.2R3-EVO, 22.3R2-EVO, 22.4R1-EVO, and all subsequent releases;

Workaround: There are no available workarounds for this issue. If LLDP and its services are not required, this issue can be mitigated by disabling LLDP.

Exploitation: Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

References

References1

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .