CVE-2026-42285 — GoBGP: Panic in AdjRib.Update via malformed BGP Update message (Nil Pointer Dereference)

Affected: osrg gobgp

GoBGP is an open source Border Gateway Protocol (BGP) implementation in the Go Programming Language. In version 4.4.0, an unauthenticated remote BGP peer can trigger a fatal panic in GoBGP by sending a specially crafted BGP UPDATE message. When the server receives a message with inconsistent attribute lengths, it improperly handles the internal state transition to a "withdraw" action, leading to a nil pointer dereference in the AdjRib.Update function. This causes the entire GoBGP process to crash, resulting in a complete loss of service availability. This issue has been patched in version 4.5.0.

GHSA-p3w2-64xm-833j — GoBGP has a panic in AdjRib.Update via malformed BGP Update message (Nil Pointer Dereference)

Affected: Go: github.com/osrg/gobgp/v4

### Summary Remote Denial of Service (DoS) via Nil Pointer Dereference in BGP Update Processing An unauthenticated remote BGP peer can trigger a fatal panic in GoBGP by sending a specially crafted BGP UPDATE message. When the server receives a message with inconsistent attribute lengths, it improperly handles the internal state transition to a "withdraw" action, leading to a nil pointer dereference in the AdjRib.Update function. This causes the entire GoBGP process to crash, resulting in a complete loss of service availability.

### Details The vulnerability originates in the interaction between the BGP message decoding logic and the Adj-RIB table management.

Triggering Condition: When a BGP UPDATE message contains attributes that fail validation (e.g., "attribute value length is short"), GoBGP logs a warning: the received Update message was treated as withdraw.

Code Path:

The message reaches github.com/osrg/gobgp/v4/pkg/server.(*peer).handleUpdate.

Due to the malformed attributes, the message is processed as a withdrawal, but the internal representation of the path or its attributes becomes nil.

The execution flows to internal/pkg/table/adj.go:127 within (*AdjRib).Update.

The Flaw: At line 127 in adj.go, the code attempts to access a member of a structure (likely the path or a specific attribute container) that is nil due to the previous validation failure.

Log Snippet: ``` {"time":"2026-04-21T12:43:10.009107962+08:00","level":"WARN","msg":"the received Update messa…

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CVE-2026-42285 — GoBGP: Panic in AdjRib.Update via malformed BGP Update message (Nil Pointer Dereference)

GHSA-p3w2-64xm-833j — GoBGP has a panic in AdjRib.Update via malformed BGP Update message (Nil Pointer Dereference)