CVE-2026-41643: GoBGP Remote Denial of Service Vulnerability in UpdatePathAttrs4ByteAs

github.com/osrg/gobgp/v4 Updated 25 Jul 2026

Summary

24/07/2026

Disclosed on

CVE-2026-41643

CVE

Yes i

Fix available

High

Severity

7.5

CVSS Score

CVE-2026-41643: GoBGP: Remote Denial of Service (Panic) in UpdatePathAttrs4ByteAs via Malformed BGP UPDATE in github.com/osrg/gobgp. Affects github.com/osrg/gobgp/v4 versions < 4.3.0. Fixed in 4.3.0. How to fix ↓

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Background

GoBGP is an open-source BGP (Border Gateway Protocol) implementation written in Go. It is designed to facilitate the management of BGP routes and is widely used in networking applications. The package provides functionalities such as route advertisement, peer management, and path attribute handling. However, it has been found to be vulnerable to a specific issue that can lead to a remote denial of service.

Vulnerability Detail

The vulnerability identified as CVE-2026-41643 occurs in the UpdatePathAttrs4ByteAs function of GoBGP when it processes malformed BGP UPDATE messages. This flaw can cause the application to panic, leading to a denial of service. Attackers can exploit this vulnerability by sending specially crafted BGP UPDATE messages to the GoBGP server, which may result in unexpected crashes and service interruptions. The affected functions include BgpServer.AddPeer, NewBgpServer, and server.AddPeer, which are critical for establishing BGP peer connections.

How To Fix

Latest published version: v4.10.0 as of 22 Oct 2026

go get github.com/osrg/gobgp/v4@v4.10.0

Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.

If you need the minimum change

4.3.0

This is the first release that contains the fix.

go get github.com/osrg/gobgp/v4@v4.3.0

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Workaround

As a temporary workaround, you can implement input validation to filter out malformed BGP UPDATE messages before they reach the GoBGP server. This can help mitigate the risk of triggering the panic condition until you can apply the patch.

Conclusion

The CVE-2026-41643 vulnerability in GoBGP poses a significant risk of remote denial of service due to the mishandling of malformed BGP UPDATE messages. It is crucial for users of the GoBGP package to update to version 4.3.0 or later to mitigate this risk. Additionally, implementing input validation can serve as a temporary measure until the update is applied.

See every vulnerability recorded for github.com/osrg/gobgp/v4 →