GoBGP confederation validation panics on empty AS_PATH attribute
위협 신호 · CVSS · EPSS · KEV
이론적 심각도 점수
예측 데이터 없음
실측 악용 기록 없음
계획된 패치 주기 내 조치(60일 이내)
CVSS 벡터 · 메트릭
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H상세 설명
Found through variant analysis based on CVE-2026-41643
Summary
GoBGP accepts a zero-length AS_PATH during UPDATE decoding and later panics while validating that attribute for a confederation eBGP peer. The vulnerable path is in the BGP UPDATE validator: a malformed UPDATE that should be rejected as a malformed AS_PATH instead reaches an unchecked p.Value[0] access, allowing a configured confederation eBGP peer to trigger a denial of service.
Affected
- Project: gobgp
- Repo: https://github.com/osrg/gobgp
- Pinned ref: c24629411ba49f160d9dc09126f418218127e016
Root cause
An established peer's receive path reads BGP bytes from the network connection in pkg/server/fsm.go:1267, parses UPDATE bodies through the BGP message decoder, and validates decoded UPDATEs with peer state at pkg/server/fsm.go:1849. The UPDATE decoder walks the path-attribute list in pkg/packet/bgp/bgp.go:15773 and selects the concrete attribute parser from the attacker-controlled attribute type at pkg/packet/bgp/bgp.go:15855. For AS_PATH, PathAttributeAsPath.DecodeFromBytes returns nil when the decoded attribute length is zero (pkg/packet/bgp/bgp.go:11533, pkg/packet/bgp/bgp.go:11538), leaving p.Value empty rather than reporting a malformed attribute. Validation then dispatches each decoded attribute through ValidateAttribute (pkg/packet/bgp/validate.go:34); in the confederation eBGP branch, pkg/packet/bgp/validate.go:162 indexes p.Value[0] before checking that any AS_PATH segment was decoded. The eBGP and confederation guards are normal peer-state gates: pkg/config/oc/util.go:127 defines eBGP as peer AS differing from local AS, pkg/config/oc/util.go:116 checks confederation membership, and pkg/server/fsm.go:740 and pkg/server/fsm.go:741 copy those results into the FSM state used by the validator.
Reproduction
INT-bgp-gobgp-confed-empty-aspath-panic.zip
1bash ./poc/run.sh 1TRIGGERED: confed empty AS_PATH validation panic: runtime error: index out of rangeThe TRIGGERED line is the recovered panic fingerprint from the confederation eBGP validation path after a zero-length AS_PATH has decoded successfully. A build failure or any output without that fingerprint would not demonstrate this bug, because the signal is tied to the unchecked AS_PATH segment access.
Impact
A remote unauthenticated peer that is configured as a confederation eBGP neighbor can establish a BGP session and send a single malformed UPDATE containing a syntactically valid AS_PATH attribute header with zero value length. Because the decode path does not turn that empty AS_PATH into a MessageError, normal malformed-attribute handling is bypassed and validation panics before GoBGP can return a BGP NOTIFICATION. The demonstrated effect is denial of service for the receive goroutine and peer session, with potential process termination if the panic is not recovered by the runtime path; no memory corruption, data disclosure, authentication bypass, or code execution is claimed.
Suggested fix
1diff --git a/pkg/packet/bgp/validate.go b/pkg/packet/bgp/validate.go 2index 2237afb..f07f4fa 100644 3--- a/pkg/packet/bgp/validate.go 4+++ b/pkg/packet/bgp/validate.go 5@@ -159,6 +159,9 @@ func ValidateAttribute(a PathAttributeInterface, rfs map[Family]BGPAddPathMode, 6 case *PathAttributeAsPath: 7 if isEBGP { 8 if isConfed { 9+ if len(p.Value) == 0 {10+ return false, NewMessageError(eCode, eSubCodeMalformedAspath, nil, "empty AS_PATH for confederation eBGP")11+ }12 if segType := p.Value[0].GetType(); segType != BGP_ASPATH_ATTR_TYPE_CONFED_SEQ {13 return false, NewMessageError(eCode, eSubCodeMalformedAspath, nil, fmt.Sprintf("segment type is not confederation seq (%d)", segType))14 }Resources
AI 심층 분석
공격 시나리오 · 재현 가능한 PoC 페이로드 · 즉시 적용 가능한 차단 패치를 한 번에 받아 보세요. 보안 운영팀이 그대로 점검·티켓팅에 쓸 수 있는 형태로 정리해 드립니다.