GHSA-8rxh-r2p6-7f2q

Описание

Summary

A remote Denial of Service (DoS) vulnerability exists in GoBGP where a malformed BGP UPDATE message can trigger a runtime error: index out of range panic. This occurs during the processing of 4-byte AS attributes when the message structure causes an internal slice index shift that is not properly handled.

Details

The vulnerability is located in internal/pkg/table/message.go within the UpdatePathAttrs4ByteAs function.

When GoBGP processes a BGP UPDATE message containing both an AS_PATH and an AS4_PATH attribute, it attempts to merge or validate them to support 4-byte AS numbers. If the attributes are ordered such that AS4_PATH (Type 17) appears before AS_PATH (Type 2), and the AS4_PATH is deemed invalid/malformed, the code attempts to remove the AS4_PATH attribute from the msg.PathAttributes slice. It appears the crash happens due to an index shift in msg.PathAttributes:

This deletion causes all subsequent attributes in the slice to shift left by one position. However, the function continues to use the original asAttrPos index (calculated before the deletion) to access or modify the AS_PATH attribute later at Line 206. Because the slice is now shorter, the "stale" index points out of bounds, triggering a panic and crashing the entire GoBGP process.

PoC

Environment: * GoBGP version: 4.2.0 Configuration: Passive peering enabled. Reproduction Steps: Configure GoBGP with a neighbor (e.g., 192.168.31.195). Send a specially crafted BGP UPDATE hex payload:

The GoBGP process will immediately crash with: panic: runtime error: index out of range [1] with length 1.

Impact

Vulnerability Type: Remote Denial of Service (DoS). Impacted Users: Any GoBGP deployment (v4.2.0 and earlier) that accepts BGP UPDATE messages from peers. Since this crash occurs in the FSM (Finite State Machine) handling loop, a single malicious peer or a malformed route propagated through a transit provider can consistently crash the BGP daemon, leading to a complete loss of routing capabilities.