---
id: CVE-2026-49837
title: >-
  GoBGP is an open source Border Gateway Protocol (BGP) implementation in the Go
  Programming Language
summary: >-
  GoBGP is an open source Border Gateway Protocol (BGP) implementation in the Go
  Programming Language. Versions prior to 4.6.0 contain a BGP OPEN capability
  parsing issue where several concrete capability decoders may parse data from
  the f…
severity: medium
cvss: 5.9
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N'
cwe:
  - CWE-125
vendor: osrg
product: gobgp
affected:
  - gobgp < 4.6.0
patched:
  - github.com/osrg/gobgp/v4 4.6.0
published: '2026-09-10'
updated: '2026-09-16'
sourceUpdated: '2026-09-16T13:42:46.953'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-49837'
references:
  - url: >-
      https://github.com/osrg/gobgp/commit/f02ca397821f6ca182ef4eb492c3cbc459552d7c
    label: security-advisories@github.com
  - url: 'https://github.com/osrg/gobgp/security/advisories/GHSA-gjrg-jjr3-56cm'
    label: security-advisories@github.com
  - url: 'https://github.com/advisories/GHSA-gjrg-jjr3-56cm'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-49837.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-49837'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2531682'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-49837'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-49837'
tags:
  - nvd
  - cve.org
  - ghsa
  - go
  - csaf
  - vex
  - red-hat
epss: 0.00332
epssPercentile: 0.23712
aliases:
  - GHSA-gjrg-jjr3-56cm
ecosystem: go
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-15T15:10:05.962553Z'
ingestedAt: '2026-07-09T23:53:27.211Z'
scores:
  nvd: 5.9
  vendor: 7.4
---

## Overview

GoBGP is an open source Border Gateway Protocol (BGP) implementation in the Go Programming Language. Versions prior to 4.6.0 contain a BGP OPEN capability parsing issue where several concrete capability decoders may parse data from the full remaining capability buffer instead of the slice bounded by the declared capability length, `CapLen`. A malformed BGP OPEN message can cause bytes from a following capability to be interpreted as part of the current capability. The most security-relevant case is the 4-octet AS capability, where a capability with `CapLen == 0` may cause the parser to read bytes from the following capability as the 4-octet AS value. This parsed value may later affect peer AS validation during BGP session establishment. Version 4.6.0 patches the issue.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-49837)

Affected packages:

- `github.com/osrg/gobgp/v4 <= 4.5.0`

Patched in:

- `github.com/osrg/gobgp/v4 4.6.0`

Source: https://github.com/advisories/GHSA-gjrg-jjr3-56cm

## Vendor advisories

- **Red Hat VEX** · Important · affected: Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat OpenShift Container Platform 4 · updated 2026-09-21 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-49837.json)