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CVE-2026-76721 – Unauthenticated RCE via Buffer Overflow – HPE Networking Instant ON (≤ 3.4.1.0)

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Summary

CVE-2026-76721 is a critical buffer overflow vulnerability in HPE Networking Instant ON that allows an unauthenticated, remote attacker to execute arbitrary code as a privileged user on the underlying operating system. HPE disclosed the flaw on September 29, 2026 as part of security bulletin HPESBNW05150, which covers five critical/high-severity issues in Instant ON access points. The issue carries a CVSS v3.1 base score of 9.8 (Critical).

Technical details

  • Root cause: A buffer overflow condition exists in a network-facing interface of HPE Networking Instant ON; input is not properly bounds-checked before being copied into a fixed-size buffer.
  • Trigger conditions: An attacker sends crafted/oversized data to the affected network interface; no authentication or user interaction is required to trigger the overflow.
  • Attack vector: Network — the vulnerability is remotely exploitable over the network with low attack complexity and no privileges required.
  • Impact: Successful exploitation can allow an attacker to execute arbitrary code as a privileged user on the underlying host, resulting in full compromise of confidentiality, integrity, and availability of the device.

Affected software

  • HPE Networking Instant ON, versions 0.0.0.0 through 3.4.1.0 (inclusive)

Severity

  • CVSS v3.1 Base Score: 9.8 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate: Update all HPE Networking Instant ON access points, switches, and Secure Gateway devices to firmware version 3.4.2 or later, as referenced in HPE security bulletin HPESBNW05150.
  • If immediate patching is not possible:
    • Ensure device management interfaces are not reachable from the public internet or from guest/untrusted networks.
    • Restrict access to management services to trusted internal networks only via firewall ACLs.
    • Isolate guest Wi-Fi and other untrusted network segments from internal management networks.

References

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