# CVE-2026-49837

## Summary

- **CVE ID:** CVE-2026-49837
- **Severity:** MEDIUM
- **CVSS Score:** 5.9 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N)
- **CWE:** CWE-125
- **Published:** Sep 10, 2026
- **Last Modified:** Sep 10, 2026

## Description

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.

## Affected Products

- osrg — gobgp (< 4.6.0)

## References

- [CNA](https://github.com/osrg/gobgp/security/advisories/GHSA-gjrg-jjr3-56cm)
- [CNA](https://github.com/osrg/gobgp/commit/f02ca397821f6ca182ef4eb492c3cbc459552d7c)

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._