# CVE-2026-49837: gobgp: GoBGP is an open source Border Gateway Protocol (BGP) implementation in the Go Programming Language

CVE-2026-49837 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-49837, released June 24, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-49837
- Priority: Routine
- CVSS: 5.9 (medium)
- EPSS: 0.0033
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | gobgp Debian 14 | 4.6.0-1 | [DEBIAN-CVE-2026-49837](https://patchblox.com/security/data/fix/linux/debian-cve-2026-49837.md) | Jun 24, 2026 |
| Linux | govulncheck-vulndb opensuse-leap 16.0 | 0.0.20260727T201416-160000.1.1 | [OPENSUSE-SU-2026:21551-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21551-1.md) | Aug 10, 2026 |
| Linux | govulncheck-vulndb sles 16.0 | 0.0.20260727T201416-160000.1.1 | [SUSE-SU-2026:23227-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23227-1.md) | Aug 10, 2026 |

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Data as of 2026-11-08T19:12:23Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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