Answer in brief
CVE-2026-49837 records a Medium severity (CVSS 5.9) vulnerability in GoBGP: BGP OPEN capability parser may read capability values outside declared CapLen boundaries. The current sources do not mark it as known exploited. The current feed maps osrg/gobgp (generic), github.com/osrg/gobgp/v4 (go). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 5.9. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps osrg/gobgp (generic), github.com/osrg/gobgp/v4 (go). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| osrg/gobgpgeneric | < 4.6.0 | Not reported |
| github.com/osrg/gobgp/v4go | <=4.5.0 | 4.6.0 |
Published upstream
Sep 10, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 16, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 10, 2026
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.
Quoted source text, attributed separately from HOL analysis.