Vulnerability-Lookup

CVE-2026-52880 (GCVE-0-2026-52880)

Vulnerability from cvelistv5 – Published: 2026-08-07 22:53 – Updated: 2026-08-11 01:22

Title

Klever-Go: REST API slow-header connection exhaustion via Gin Engine.Run

Summary

Klever-Go is the Go implementation of the Klever blockchain protocol. Versions from 1.7.14 through 1.7.17 are vulnerable to a remotely triggerable denial of service. Both REST APIs are started with the Gin Engine.Run convenience method, which serves requests through Go's default HTTP server with no ReadHeaderTimeout, ReadTimeout, or MaxHeaderBytes configured. As a result, incoming connections that never complete their request headers are held open indefinitely. When a REST listener is reachable beyond localhost through the documented all-interface bind or a Docker port-publish deployment, a single unauthenticated client can open many slow-header connections and hold them open until server file descriptors are exhausted, preventing the API from accepting new connections. This renders the REST API unavailable to legitimate clients. This issue is fixed in version 1.7.18.

Severity

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-11 01:21 UTC

CWE

CWE-400 - Uncontrolled Resource Consumption
CWE-770 - Allocation of Resources Without Limits or Throttling

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7895 records in the last 180 days details

References

2 references

URL	Tags
https://github.com/klever-io/klever-go/security/a…	x_refsource_CONFIRM
https://github.com/klever-io/klever-go/releases/t…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
klever-io	klever-go	Affected: >= 1.7.14, < 1.7.18	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-52880

Vulnerability from fkie_nvd - Published: 2026-08-07 23:17 - Updated: 2026-10-24 16:10

Severity

7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/klever-io/klever-go/releases/tag/v1.7.18
	security-advisories@github.com	https://github.com/klever-io/klever-go/security/advisories/GHSA-w4c6-7r69-w7j9
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/klever-io/klever-go/security/advisories/GHSA-w4c6-7r69-w7j9

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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    },
    {
      "lang": "es",
      "value": "Klever-Go es la implementaci\u00f3n en Go del protocolo blockchain de Klever. Las versiones desde la 1.7.14 hasta la 1.7.17 son vulnerables a una denegaci\u00f3n de servicio que puede ser activada remotamente. Ambas APIs REST se inician con el m\u00e9todo de conveniencia Gin Engine.Run, que atiende solicitudes a trav\u00e9s del servidor HTTP predeterminado de Go sin ReadHeaderTimeout, ReadTimeout o MaxHeaderBytes configurados. Como resultado, las conexiones entrantes que nunca completan sus encabezados de solicitud se mantienen abiertas indefinidamente. Cuando un oyente REST es accesible m\u00e1s all\u00e1 de localhost a trav\u00e9s del enlace de todas las interfaces documentado o una implementaci\u00f3n de publicaci\u00f3n de puerto de Docker, un \u00fanico cliente no autenticado puede abrir muchas conexiones de encabezado lento y mantenerlas abiertas hasta que los descriptores de archivo del servidor se agoten, impidiendo que la API acepte nuevas conexiones. Esto hace que la API REST no est\u00e9 disponible para clientes leg\u00edtimos. Este problema est\u00e1 solucionado en la versi\u00f3n 1.7.18."
    }
  ],
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  "lastModified": "2026-10-24T16:10:00.153",
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GHSA-W4C6-7R69-W7J9

Vulnerability from github – Published: 2026-06-05 16:41 – Updated: 2026-06-09 18:40

Summary

klever-go: REST API slow-header connection exhaustion via Gin Engine.Run

Details

Summary

The Klever seednode REST API starts a Gin engine with Engine.Run(restAPIInterface). In Gin v1.9.1, Engine.Run calls Go's default http.ListenAndServe, which constructs an HTTP server without application-level ReadHeaderTimeout, ReadTimeout, or MaxHeaderBytes limits.

An unauthenticated client that can reach a REST listener bound with Klever's documented --rest-api-interface :8080 all-interface option can hold incomplete HTTP headers open indefinitely. In a local proof against the real cmd/seednode/api.Start path on v1.7.17, 120 slow-header connections caused 20/20 legitimate /log probes to fail with accept: too many open files. A fixed control using the same Gin router behind an explicit http.Server with ReadHeaderTimeout, ReadTimeout, and MaxHeaderBytes retained 0 slow connections and served 20/20 probes.

This report is distinct from the P2P advisories and from my direct-message goroutine report. This finding concerns Klever-owned HTTP REST startup code (cmd/seednode/api and network/api) using Gin Engine.Run without server-level header deadlines. It does not depend on MultiDataInterceptor, Batch.Decompress, libp2p, malformed P2P messages, or direct-message goroutine spawning.

Details

Seednode REST API, latest release v1.7.17:

cmd/seednode/api/api.go:17 defines Start(restAPIInterface, marshalizer).
cmd/seednode/api/api.go:18 creates ws := gin.Default().
cmd/seednode/api/api.go:23 returns ws.Run(restAPIInterface).
cmd/seednode/CLI.md:23 documents --rest-api-interface; it says :8080 binds all interfaces and off disables the API.

Node REST API, latest release v1.7.17:

network/api/api.go:79 creates ws = gin.Default().
network/api/api.go:98 returns ws.Run(kleverFacade.RestAPIInterface()).
cmd/node/main.go:147-150 documents the same --rest-api-interface flag and says :8080 binds all interfaces.
docker/README.md:56-61 and docker/README.md:67-70 publish host port 8080 for full-node and validator Docker examples.
README.md:264-268 documents that the node exposes a REST API for blockchain queries and operations.

The seednode REST API source is byte-identical across v1.7.14 through v1.7.17; the captured runtime PoC was executed on v1.7.17.

Current develop commit 10bcfd50 remains affected:

network/api/api.go:98 still returns ws.Run(kleverFacade.RestAPIInterface()).
cmd/seednode/api/api.go:59 still returns ws.Run(restAPIInterface).

Gin v1.9.1 implements Engine.Run as:

func (engine *Engine) Run(addr ...string) (err error) {
    address := resolveAddress(addr)
    err = http.ListenAndServe(address, engine.Handler())
    return
}

In my source sweep, I did not find a production http.Server{ReadHeaderTimeout: ...} wrapper for either REST start path. The only ReadHeaderTimeout hit I found in the repository was a test helper under network/api/websocket/routes_test.go.

PoC

GitHub Private Vulnerability Reporting does not appear to allow file attachments in this form, so I am including the reproduction command and captured output inline. I can paste the full 254-line Go test patch in a reply immediately if useful.

The test starts two local child servers:

Vulnerable: the real cmd/seednode/api.Start path.
Fixed control: the same Gin router served through http.Server{ReadHeaderTimeout: 250ms, ReadTimeout: 250ms, MaxHeaderBytes: 4096}.

Reproduction from a clean checkout:

git clone https://github.com/klever-io/klever-go
cd klever-go
git checkout v1.7.17

# Apply the PoC patch to cmd/seednode/api.
# I can provide the full patch in this advisory thread.

go test ./cmd/seednode/api -run TestPoC_SeednodeAPISlowlorisDifferential -count=1 -v -timeout 60s

Captured output on v1.7.17:

POC_RESULT mode=vulnerable slow_connections_opened=120 slow_connections_still_open=111 legitimate_probe_ok=0 legitimate_probe_fail=20
POC_RESULT mode=fixed slow_connections_opened=120 slow_connections_still_open=0 legitimate_probe_ok=20 legitimate_probe_fail=0

The vulnerable server also logs repeated accept failures:

http: Accept error: accept tcp 127.0.0.1:56415: accept: too many open files; retrying in 1s

Impact

For an externally reachable Klever REST listener, a single unauthenticated client can retain many server-side connections by never completing HTTP headers. Because the Go server has no read-header deadline, those connections persist until the client closes them or an external proxy/firewall intervenes.

The direct result is REST API unavailability for legitimate clients. The local proof demonstrates this as 0/20 legitimate /log probes succeeding while the vulnerable server is saturated, versus 20/20 succeeding with the fixed server wrapper.

I am not claiming default public internet exposure. The default bind is localhost:8080. The affected condition is a REST API listener exposed through Klever's documented all-interface bind or Docker port-publish deployment shape.

This maps to the SECURITY.md High category: "Denial of Service affecting network availability." If Klever treats externally reachable REST API unavailability as non-critical because the default bind is localhost, the conservative classification is Medium under "Performance degradation attacks" / "Non-critical DoS vectors."

All testing was local loopback only. I did not contact Klever mainnet, public testnet, hosted RPCs, explorers, or third-party production infrastructure.

Suggested fix:

Start both REST APIs through explicit http.Server values instead of Engine.Run, for example:

srv := &http.Server{
    Addr:              restAPIInterface,
    Handler:           ws.Handler(),
    ReadHeaderTimeout: 5 * time.Second,
    ReadTimeout:       10 * time.Second,
    WriteTimeout:      30 * time.Second,
    IdleTimeout:       120 * time.Second,
    MaxHeaderBytes:    32 << 10,
}
return srv.ListenAndServe()

Apply the same pattern to:

cmd/seednode/api.Start
network/api.Start

If Klever expects deployments to expose the REST API through a reverse proxy, I still recommend setting server-level limits in the application. That keeps the binary safe when operators use the documented direct bind or Docker port-publish path.

Severity

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.7.17"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/klever-io/klever-go"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.7.14"
            },
            {
              "fixed": "1.7.18"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-52880"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400",
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-05T16:41:58Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Summary\n\nThe Klever seednode REST API starts a Gin engine with `Engine.Run(restAPIInterface)`. In Gin v1.9.1, `Engine.Run` calls Go\u0027s default `http.ListenAndServe`, which constructs an HTTP server without application-level `ReadHeaderTimeout`, `ReadTimeout`, or `MaxHeaderBytes` limits.\n\nAn unauthenticated client that can reach a REST listener bound with Klever\u0027s documented `--rest-api-interface :8080` all-interface option can hold incomplete HTTP headers open indefinitely. In a local proof against the real `cmd/seednode/api.Start` path on `v1.7.17`, 120 slow-header connections caused 20/20 legitimate `/log` probes to fail with `accept: too many open files`. A fixed control using the same Gin router behind an explicit `http.Server` with `ReadHeaderTimeout`, `ReadTimeout`, and `MaxHeaderBytes` retained 0 slow connections and served 20/20 probes.\n\nThis report is distinct from the P2P advisories and from my direct-message goroutine report. This finding concerns Klever-owned HTTP REST startup code (`cmd/seednode/api` and `network/api`) using Gin `Engine.Run` without server-level header deadlines. It does not depend on `MultiDataInterceptor`, `Batch.Decompress`, libp2p, malformed P2P messages, or direct-message goroutine spawning.\n\n### Details\n\nSeednode REST API, latest release `v1.7.17`:\n\n- `cmd/seednode/api/api.go:17` defines `Start(restAPIInterface, marshalizer)`.\n- `cmd/seednode/api/api.go:18` creates `ws := gin.Default()`.\n- `cmd/seednode/api/api.go:23` returns `ws.Run(restAPIInterface)`.\n- `cmd/seednode/CLI.md:23` documents `--rest-api-interface`; it says `:8080` binds all interfaces and `off` disables the API.\n\nNode REST API, latest release `v1.7.17`:\n\n- `network/api/api.go:79` creates `ws = gin.Default()`.\n- `network/api/api.go:98` returns `ws.Run(kleverFacade.RestAPIInterface())`.\n- `cmd/node/main.go:147-150` documents the same `--rest-api-interface` flag and says `:8080` binds all interfaces.\n- `docker/README.md:56-61` and `docker/README.md:67-70` publish host port `8080` for full-node and validator Docker examples.\n- `README.md:264-268` documents that the node exposes a REST API for blockchain queries and operations.\n\nThe seednode REST API source is byte-identical across `v1.7.14` through `v1.7.17`; the captured runtime PoC was executed on `v1.7.17`.\n\nCurrent `develop` commit `10bcfd50` remains affected:\n\n- `network/api/api.go:98` still returns `ws.Run(kleverFacade.RestAPIInterface())`.\n- `cmd/seednode/api/api.go:59` still returns `ws.Run(restAPIInterface)`.\n\nGin v1.9.1 implements `Engine.Run` as:\n\n```go\nfunc (engine *Engine) Run(addr ...string) (err error) {\n    address := resolveAddress(addr)\n    err = http.ListenAndServe(address, engine.Handler())\n    return\n}\n```\n\nIn my source sweep, I did not find a production `http.Server{ReadHeaderTimeout: ...}` wrapper for either REST start path. The only `ReadHeaderTimeout` hit I found in the repository was a test helper under `network/api/websocket/routes_test.go`.\n\n### PoC\n\nGitHub Private Vulnerability Reporting does not appear to allow file attachments in this form, so I am including the reproduction command and captured output inline. I can paste the full 254-line Go test patch in a reply immediately if useful.\n\nThe test starts two local child servers:\n\n1. Vulnerable: the real `cmd/seednode/api.Start` path.\n2. Fixed control: the same Gin router served through `http.Server{ReadHeaderTimeout: 250ms, ReadTimeout: 250ms, MaxHeaderBytes: 4096}`.\n\nReproduction from a clean checkout:\n\n```bash\ngit clone https://github.com/klever-io/klever-go\ncd klever-go\ngit checkout v1.7.17\n\n# Apply the PoC patch to cmd/seednode/api.\n# I can provide the full patch in this advisory thread.\n\ngo test ./cmd/seednode/api -run TestPoC_SeednodeAPISlowlorisDifferential -count=1 -v -timeout 60s\n```\n\nCaptured output on `v1.7.17`:\n\n```text\nPOC_RESULT mode=vulnerable slow_connections_opened=120 slow_connections_still_open=111 legitimate_probe_ok=0 legitimate_probe_fail=20\nPOC_RESULT mode=fixed slow_connections_opened=120 slow_connections_still_open=0 legitimate_probe_ok=20 legitimate_probe_fail=0\n```\n\nThe vulnerable server also logs repeated accept failures:\n\n```text\nhttp: Accept error: accept tcp 127.0.0.1:56415: accept: too many open files; retrying in 1s\n```\n\n### Impact\n\nFor an externally reachable Klever REST listener, a single unauthenticated client can retain many server-side connections by never completing HTTP headers. Because the Go server has no read-header deadline, those connections persist until the client closes them or an external proxy/firewall intervenes.\n\nThe direct result is REST API unavailability for legitimate clients. The local proof demonstrates this as 0/20 legitimate `/log` probes succeeding while the vulnerable server is saturated, versus 20/20 succeeding with the fixed server wrapper.\n\nI am not claiming default public internet exposure. The default bind is `localhost:8080`. The affected condition is a REST API listener exposed through Klever\u0027s documented all-interface bind or Docker port-publish deployment shape.\n\nThis maps to the `SECURITY.md` High category: \"Denial of Service affecting network availability.\" If Klever treats externally reachable REST API unavailability as non-critical because the default bind is localhost, the conservative classification is Medium under \"Performance degradation attacks\" / \"Non-critical DoS vectors.\"\n\nAll testing was local loopback only. I did not contact Klever mainnet, public testnet, hosted RPCs, explorers, or third-party production infrastructure.\n\nSuggested fix:\n\nStart both REST APIs through explicit `http.Server` values instead of `Engine.Run`, for example:\n\n```go\nsrv := \u0026http.Server{\n    Addr:              restAPIInterface,\n    Handler:           ws.Handler(),\n    ReadHeaderTimeout: 5 * time.Second,\n    ReadTimeout:       10 * time.Second,\n    WriteTimeout:      30 * time.Second,\n    IdleTimeout:       120 * time.Second,\n    MaxHeaderBytes:    32 \u003c\u003c 10,\n}\nreturn srv.ListenAndServe()\n```\n\nApply the same pattern to:\n\n- `cmd/seednode/api.Start`\n- `network/api.Start`\n\nIf Klever expects deployments to expose the REST API through a reverse proxy, I still recommend setting server-level limits in the application. That keeps the binary safe when operators use the documented direct bind or Docker port-publish path.",
  "id": "GHSA-w4c6-7r69-w7j9",
  "modified": "2026-06-09T18:40:44Z",
  "published": "2026-06-05T16:41:58Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/klever-io/klever-go/security/advisories/GHSA-w4c6-7r69-w7j9"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/klever-io/klever-go"
    },
    {
      "type": "WEB",
      "url": "https://github.com/klever-io/klever-go/releases/tag/v1.7.18"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "klever-go: REST API slow-header connection exhaustion via Gin Engine.Run"
}

Sightings

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Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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CVE-2026-52880 (GCVE-0-2026-52880)

FKIE_CVE-2026-52880

GHSA-W4C6-7R69-W7J9

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