# CVE-2026-125406: Ettercap through 0.8.4.1 Stack Buffer Underwrite via Telnet Dissector Backspace Handling

Status: published. Published: 2026-11-09. Updated: 2026-11-09.

Ettercap through 0.8.4.1 contains a stack buffer underwrite vulnerability in the telnet dissector in src/dissectors/ec_telnet.c that decrements the output pointer on backspace without a lower bound check. Attackers can send a telnet stream with more backspaces than preceding characters to write below the stack buffer, corrupting the stack of the Ettercap process that normally runs as root.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/Ettercap/ettercap/commit/1d8badb713579419a29a494bb463a1af59707e98
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/Ettercap/ettercap/pull/1330

## Affected products and versions

- Ettercap / ettercap (Ettercap/ettercap): ≥ 0; ≤ 0.8.4.1 (affected, custom). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 8.7 (high); CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 8.8 (high); CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-124

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/Ettercap/ettercap/security/advisories/GHSA-w5ch-7c4x-crcc (CNA: VulnCheck; vendor-advisory)

- https://github.com/Ettercap/ettercap/commit/1d8badb713579419a29a494bb463a1af59707e98 (CNA: VulnCheck; patch)

- https://github.com/Ettercap/ettercap/pull/1330 (CNA: VulnCheck; issue-tracking, patch)

- https://github.com/Ettercap/ettercap/blob/v0.8.4.1/src/dissectors/ec_telnet.c#L150-L159 (CNA: VulnCheck; technical-description)

- https://www.vulncheck.com/advisories/ettercap-through-0.8.4.1-stack-buffer-underwrite-via-telnet-dissector-backspace-handling (CNA: VulnCheck; third-party-advisory)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-125406; retrieved 2026-11-10; source updated 2026-11-09

Revision: 2d8138778b02be9791aa970678f592a78eace699e5235e89ec271b60da8eb09b

Canonical: https://y2.dev/cve/CVE-2026-125406

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.