emp3r0r has an unauthenticated HTTP Polling DoS

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

emp3r0r is a C2 designed by Linux users for Linux environments. Prior to version 4.2.5, the `http_poll` C2 transport accepts attacker-controlled HTTP polling sessions before CBOR `MsgAuth` authentication is completed. A remote unauthenticated attacker can create arbitrary polling sessions and send request bodies that are forwarded into the C2 dispatch path. This can consume server resources and trigger pre-auth C2 processing. Version 4.2.5 patches the issue.

Source published

15 Sep 2026 20:48:05 UTC

Source modified

16 Sep 2026 17:59:54 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

emp3r0r is a C2 designed by Linux users for Linux environments. Prior to version 4.2.5, the `http_poll` C2 transport accepts attacker-controlled HTTP polling sessions before CBOR `MsgAuth` authentication is completed. A remote unauthenticated attacker can create arbitrary polling sessions and send request bodies that are forwarded into the C2 dispatch path. This can consume server resources and trigger pre-auth C2 processing. Version 4.2.5 patches the issue.

Source published

Sep 15, 2026, 8:48:05 PM (timezone not stated)

Source modified

Sep 16, 2026, 5:59:54 PM (timezone not stated)

Observed here

11 Nov 2026 15:02:40 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 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

emp3r0r is a C2 designed by Linux users for Linux environments. Prior to version 4.2.5, the `http_poll` C2 transport accepts attacker-controlled HTTP polling sessions before CBOR `MsgAuth` authentication is completed. A remote unauthenticated attacker can create arbitrary polling sessions and send request bodies that are forwarded into the C2 dispatch path. This can consume server resources and trigger pre-auth C2 processing. Version 4.2.5 patches the issue.

Source published

15 Sep 2026 21:16:41 UTC

Source modified

30 Sep 2026 17:51:56 UTC

Observed here

25 Oct 2026 14:19:22 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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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: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

### Summary The `http_poll` C2 transport accepts attacker-controlled HTTP polling sessions before CBOR `MsgAuth` authentication is completed. A remote unauthenticated attacker can create arbitrary polling sessions and send request bodies that are forwarded into the C2 dispatch path. This can consume server resources and trigger pre-auth C2 processing. ### Details The plain HTTP C2 server starts the HTTP polling listener and forwards requests into `HandleHTTPServerSession`: ```go // core/internal/cc/server/c2_http_server.go mux.HandleFunc(c2Path, func(w http.ResponseWriter, req *http.Request) { stream, err := transport.HandleHTTPServerSession(w, req, &live.RuntimeConfig.MalleableC2) ... if stream != nil { go cborStreamAccept(transport.NewStreamTransport(stream, req.RemoteAddr)) } }) ``` The HTTP polling handler accepts an attacker-supplied `sessionID` and `init=1` cookie, then creates and stores a server-side stream before authentication: ```go // core/internal/transport/c2channel_http.go if isInit { stream = newHTTPServerStream(sessionID) w.WriteHeader(http.StatusOK) return stream, nil } ``` POST bodies for that unauthenticated session are read and queued before CBOR authentication rejects them: ```go // core/internal/transport/c2channel_http.go case http.MethodPost: data, err := io.ReadAll(req.Body) if err == nil && len(data) > 0 { select { case stream.readCh <- data: w.WriteHeader(http.StatusOK) ... } } ``` Authentication only happens later in the C2 dispatch layer: ```go // core/internal/cc/server/dispatcher.go secureConn := transport.NewSecureConn(t) ... n, err := secureConn.Read(authFrame) ``` ### PoC 1. Start the C2 server in a lab environment with the HTTP polling transport exposed, for example with `--http-port 12345`. 2. Send an unauthenticated HTTP POST to the default polling path `/api/v1/telemetry` with a random `sessionID` cookie and the `init=1` cookie value. 3. Send a second unauthenticated HTTP POST to `/api/v1/telemetry` using the same `sessionID`, with a request body containing repeated `A` bytes. 4. Observe that both unauthenticated requests return HTTP `200`. 5. Observe the C2 server log showing attacker-controlled bytes reaching the encrypted C2 frame parser, for example: `read: invalid encrypted chunk length: 1094795585`. 6. `1094795585` is `0x41414141`, which corresponds to `AAAA`, confirming unauthenticated request body data reached `cborProtocolDispatch` before CBOR `MsgAuth` authentication. 7. Repeat the request sequence concurrently to increase server resource usage and log volume. ### Impact - Remote unauthenticated attackers can create arbitrary HTTP polling sessions. - Attacker-controlled request bodies reach pre-auth C2 dispatch handling. - Repeated requests can consume server memory, goroutines, request handling capacity, and log volume. - C2 service availability and operator reliability may be degraded under sustained traffic. ### Remediation - Require authentication before creating long-lived HTTP polling sessions. - Do not forward request bodies into the C2 stream before validation. - Add strict request body limits.

Source published

15 Sep 2026 20:47:17 UTC

Source modified

28 Sep 2026 17:10:43 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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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: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Publisher rating · HIGH

emp3r0r has an unauthenticated HTTP Polling DoS in github.com/jm33-m0/emp3r0r/core

Source published

28 Sep 2026 16:43:40 UTC

Source modified

28 Sep 2026 17:00:16 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.