{"id":"GHSA-frrj-87jh-2772","revision":null,"records":[{"revision":"db0cca618e9f4c3eae59a4125b4304a1","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-49838","aliases":[],"title":"GoBGP confederation validation panics on empty AS_PATH attribute","description":"GoBGP is an open source Border Gateway Protocol (BGP) implementation in the Go Programming Language. Prior to version 4.7.0, 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. 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Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-49838","identifiers":["CVE-2026-49838"]},"retained":false,"historicalAffected":[]},{"revision":"03a7ce4bc29842cdad088fc8a705df55","observedAt":"2026-10-24T13:19:41.952+00:00","statement":{"source":"osv","id":"GHSA-frrj-87jh-2772","aliases":["CVE-2026-49838","GO-2026-5954"],"title":"GoBGP confederation validation panics on empty AS_PATH attribute","description":"Found through variant analysis based on `CVE-2026-41643`\n\n## Summary\nGoBGP 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.\n\n## Affected\n- Project: gobgp\n- Repo: https://github.com/osrg/gobgp\n- Pinned ref: c24629411ba49f160d9dc09126f418218127e016\n\n## Root cause\nAn 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.\n\n## Reproduction\n\n[INT-bgp-gobgp-confed-empty-aspath-panic.zip](https://github.com/user-attachments/files/28203698/INT-bgp-gobgp-confed-empty-aspath-panic.zip)\n\n```bash\nbash ./poc/run.sh\n```\n\n```text\nTRIGGERED: confed empty AS_PATH validation panic: runtime error: index out of range\n```\n\nThe `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.\n\n## Impact\nA 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.\n\n## Suggested fix\n```001-fix.diff\ndiff --git a/pkg/packet/bgp/validate.go b/pkg/packet/bgp/validate.go\nindex 2237afb..f07f4fa 100644\n--- a/pkg/packet/bgp/validate.go\n+++ b/pkg/packet/bgp/validate.go\n@@ -159,6 +159,9 @@ func ValidateAttribute(a PathAttributeInterface, rfs map[Family]BGPAddPathMode,\n \tcase *PathAttributeAsPath:\n \t\tif isEBGP {\n \t\t\tif isConfed {\n+\t\t\t\tif len(p.Value) == 0 {\n+\t\t\t\t\treturn false, NewMessageError(eCode, eSubCodeMalformedAspath, nil, \"empty AS_PATH for confederation eBGP\")\n+\t\t\t\t}\n \t\t\t\tif segType := p.Value[0].GetType(); segType != BGP_ASPATH_ATTR_TYPE_CONFED_SEQ {\n \t\t\t\t\treturn false, NewMessageError(eCode, eSubCodeMalformedAspath, nil, fmt.Sprintf(\"segment type is not confederation seq (%d)\", segType))\n \t\t\t\t}\n```\n\n## Resources\n- https://github.com/osrg/gobgp/blob/c24629411ba49f160d9dc09126f418218127e016/pkg/packet/bgp/bgp.go#L11533-L11540\n- https://github.com/osrg/gobgp/blob/c24629411ba49f160d9dc09126f418218127e016/pkg/packet/bgp/validate.go#L159-L164","state":0,"publishedAt":"2026-07-09T23:21:05+00:00","modifiedAt":"2026-09-10T03:50:51.9480302+00:00","affected":[{"ecosystem":"Go","name":"github.com/osrg/gobgp/v4","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"4.7.0"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"MODERATE"}],"references":["https://github.com/osrg/gobgp/security/advisories/GHSA-frrj-87jh-2772","https://github.com/osrg/gobgp"],"sourceUrl":"https://github.com/advisories/GHSA-frrj-87jh-2772","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-frrj-87jh-2772","identifiers":["GHSA-frrj-87jh-2772","CVE-2026-49838","GO-2026-5954"]},"retained":false,"historicalAffected":[]},{"revision":"d5b6db4ae01d4803b2a55f35a1a85e61","observedAt":"2026-10-24T13:19:41.952+00:00","statement":{"source":"osv","id":"GO-2026-5954","aliases":["CVE-2026-49838","GHSA-frrj-87jh-2772"],"title":"GoBGP confederation validation panics on empty AS_PATH attribute in github.com/osrg/gobgp","description":"GoBGP confederation validation panics on empty AS_PATH attribute in github.com/osrg/gobgp","state":0,"publishedAt":"2026-07-24T18:35:55+00:00","modifiedAt":"2026-07-24T19:00:28.0292674+00:00","affected":[{"ecosystem":"Go","name":"github.com/osrg/gobgp/v4","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"4.7.0"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[],"references":["https://github.com/osrg/gobgp/security/advisories/GHSA-frrj-87jh-2772","https://github.com/osrg/gobgp/commit/4a319a6c25630fb3cdbda3e9ccfe56e702bdaaa0"],"sourceUrl":"https://osv.dev/vulnerability/GO-2026-5954","license":"OSV · upstream source license applies","key":"osv:GO-2026-5954","identifiers":["GO-2026-5954","CVE-2026-49838","GHSA-frrj-87jh-2772"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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