CVE-2026-49837 Details
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.
A parsing vulnerability has been identified in GoBGP, an open-source BGP implementation in Go, affecting versions through 4.5.0. The issue arises in the BGP OPEN capability parser, where certain capability decoders may incorrectly read data from the entire remaining capability buffer instead of the portion limited by the declared capability length, 'CapLen'. This flaw can be exploited by sending a malformed BGP OPEN message, causing bytes from a subsequent capability to be misinterpreted as part of the current one. The most significant impact occurs with the 4-octet AS capability, where a 'CapLen' of 0 can lead the parser to read bytes from the following capability as the AS value. This misread value can subsequently influence peer AS validation during BGP session establishment.
Users can upgrade to GoBGP version 4.6.0 or later, where this vulnerability has been patched.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Sep 10, 2026CISA-ADP
Assessed Sep 15, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/osrg/gobgp/commit/f02ca397821f6ca182ef4eb492c3cbc459552d7c | [email protected] | Source CodeVendor |
| https://github.com/osrg/gobgp/security/advisories/GHSA-gjrg-jjr3-56cm | [email protected] | AdvisoryRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-125 | Out-of-bounds Read | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| GoBGP | <= 4.5.0 (semver) |
CPE
Remediation
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 15, 2026 | CVE Modified | CISA-ADP |
| Sep 10, 2026 | New CVE Received | [email protected] |