CVE-2026-76661

Executive Summary

CVE-2026-76661 is a vulnerability in HPE NonStop QIOMON that permits an out-of-bounds write, allowing an attacker to corrupt buffer data. The flaw is remotely reachable (AV:N), requires low privileges (PR:L), and depends on user interaction (UI:R), with high impact to integrity and availability. No public exploit, PoC, or Nuclei template exists, and no vendor patch is currently confirmed; EPSS has not yet scored this CVE.

Technical Analysis

HPE NonStop QIOMON is a subsystem associated with the NonStop operating environment. Per the NVD description, the vulnerability is an out-of-bounds write that "can corrupt buffer data." This maps to CWE-20 (Improper Input Validation) in the CNA-supplied weakness mapping: insufficient validation of input leads to memory being written outside the intended buffer boundary.

Out-of-bounds writes occur when an application computes a destination or length incorrectly, or fails to bound-check an externally influenced value before copying data into a fixed or dynamically sized buffer. The resulting memory corruption can overwrite adjacent memory structures, leading to data integrity loss, malformed internal state, and potentially availability failures (crash or abort of the affected component). Because the CVE is mapped to CWE-20 rather than a memory-corruption-specific CWE, the root cause is characterized as a validation weakness at the input-handling layer of QIOMON.

Attack surface: the CVSS vector indicates network accessibility (AV:N), meaning the vulnerable component is reachable over a network path. The vector also indicates PR:L (low privileges required) and UI:R (user interaction required). This implies that a low-privileged actor — or a user on the local/adjacent network path — must perform some action (for example, submitting input or interacting with the QIOMON service) for the write to be triggered.

Impact per CVSS subscores: Integrity is rated High (I:H), Availability is rated High (A:H), and Confidentiality is Low (C:L). The write corrupts buffer content, which drives the integrity rating; adjacent memory corruption can drive availability loss. Confidentiality impact is limited, consistent with an out-of-bounds write that corrupts data rather than directly disclosing it.

No public PoC exists. No Nuclei template exists. No exploit code has been observed. No affected version range, package manifest, or OSV package data was supplied. The precise input vector, protocol, and triggering condition are not disclosed in the available description; the analysis above is limited to the vulnerability class (input-validation-driven out-of-bounds write) and the CVSS-derived exposure profile.

Exploitation Scenarios

No public PoC is available; the attack chain below is inferred strictly from the vulnerability class and CVSS metrics.

1. Reconnaissance / target identification. An attacker identifies reachable HPE NonStop QIOMON services on a network. Since the vector is AV:N and PR:L, the attacker requires either network access to the QIOMON interface or low-privileged access to the NonStop environment.

2. Triggering the flaw. The vulnerability class is an out-of-bounds write caused by improper input validation. The attacker supplies crafted input to the QIOMON component through its available interaction interface. Because UI:R is indicated, the attack path likely requires a user (or an automated low-privileged process acting on the user's behalf) to submit or process the malicious input. The malformed/oversized/unexpected input is handled without adequate bounds checking, causing data to be written past the end (or before the start) of the intended buffer.

3. Payload-level execution. At the vulnerability-class level, the payload is an input value crafted to exceed or violate the buffer's expected bounds, causing memory writes beyond the allocated region. No specific function names, parameters, or endpoints are disclosed by the description; the concrete trigger cannot be enumerated from available data. An attacker would iteratively adjust the input to control the extent of the out-of-bounds write and corrupt adjacent memory.

4. Post-exploitation impact. Successful corruption produces altered buffer content and potentially damaged adjacent memory structures. This yields integrity and availability impact consistent with CVSS I:H/A:H, and limited confidentiality impact (C:L). Depending on what memory is adjacent to the corrupted buffer, outcomes may range from incorrect processing results to component crashes or denial of service. No evidence indicates exploit code achieving code execution has been observed publicly.

Impact Assessment

• Confidentiality (C:L): Limited exposure; the out-of-bounds write corrupts data more than it discloses it.
• Integrity (I:H): High. Buffer corruption directly alters data and internal state.
• Availability (A:H): High. Memory corruption can crash or destabilize the affected QIOMON component.
• Scope (S:U): Impact is confined to the vulnerable component's security authority.
• Attack vector (AV:N): Remotely reachable.
• Privileges required (PR:L): Attacker needs low privileges.
• User interaction (UI:R): Exploitation depends on a user/process action.

Business impact centers on reliability and data integrity of HPE NonStop environments that expose QIOMON. NonStop systems commonly support transaction processing, payment, and other high-availability workloads; corruption or crash of a QIOMON component can affect dependent services and availability SLAs. Blast radius is bounded to QIOMON's authority (Scope:U) but can extend operationally to anything relying on the affected subsystem. The requirement for low privileges and user interaction somewhat constrains mass-exploitation potential, but targeted attacks against exposed NonStop management/service interfaces remain feasible.

Detection Guidance

Sigma Rule

title: Potential HPE NonStop QIOMON Out-of-Bounds Write Attempt
id: 9c2b1f47-3a6e-4d9b-8f21-76661cve0001
status: experimental
description: Detects anomalous or malformed input targeting HPE NonStop QIOMON that may indicate attempts to trigger CVE-2026-76661 (out-of-bounds write / buffer corruption).
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-76661
author: valtersit.com
date: 2026/01/01
logsource:
  product: hpe
  service: nonstop
detection:
  selection_process:
    Image|endswith:
      - '\QIOMON'
      - '/QIOMON'
  selection_crash:
    EventID:
      - 1000
      - 1001
    Provider_Name: 'Application Error'
  selection_buffer:
    Message|contains:
      - 'buffer overflow'
      - 'out-of-bounds'
      - 'memory corruption'
      - 'QIOMON'
  condition: selection_process and (selection_crash or selection_buffer)
falsepositives:
  - Legitimate QIOMON maintenance operations
  - Vendor diagnostic tooling
level: high

YARA Rule

rule CVE_2026_76661_HPE_NonStop_QIOMON_OOB_Write
{
    meta:
        description = "Detects artifacts consistent with CVE-2026-76661, an out-of-bounds write in HPE NonStop QIOMON capable of corrupting buffer data."
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-76661"
        author = "valtersit.com"
        date = "2026-01-01"
        severity = "high"
        cve = "CVE-2026-76661"

    strings:
        $q = "QIOMON" ascii wide nocase
        $b1 = "buffer overflow" ascii wide nocase
        $b2 = "out-of-bounds write" ascii wide nocase
        $b3 = "buffer corrupt" ascii wide nocase

    condition:
        $q and any of ($b*)
}

Suricata IDS Rule

alert tcp any any -> any any (msg:"CVE-2026-76661 HPE NonStop QIOMON potential out-of-bounds write / buffer corruption attempt"; flow:to_server,established; content:"QIOMON"; nocase; threshold:type both, track by_src, count 20, seconds 60; classtype:attempted-admin; reference:cve,2026-76661; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-76661; sid:202676661; rev:1;)

Elastic Detection

process where host.os.type == "windows" or host.os.type == "linux"
and process.name like~ "*QIOMON*"
and (
  process.args like~ "*buffer*" or
  process.args like~ "*overflow*" or
  process.args like~ "*%00*"
)

Splunk SPL Query

index=* (sourcetype=*nonstop* OR sourcetype=*hpe* OR source=*QIOMON*)
("QIOMON" OR "out-of-bounds" OR "buffer overflow" OR "memory corruption")
| stats count values(host) as hosts values(source) as sources by _time, message
| where count > 5
| sort - _time

Wazuh OSSEC Rule

<group name="hpe,nonstop,qiomon,">
  <rule id="2026766" level="12">
    <decoded_as>json</decoded_as>
    <match>QIOMON</match>
    <regex>out-of-bounds|buffer overflow|memory corruption</regex>
    <description>CVE-2026-76661: Possible HPE NonStop QIOMON out-of-bounds write / buffer corruption attempt detected</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>cve_2026_76661,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source).

1. Immediate mitigations:

   • Restrict network access to HPE NonStop QIOMON interfaces to trusted management networks and specific systems; do not expose QIOMON broadly.
   • Enforce least privilege to reduce the low-privilege (PR:L) attack surface.
   • Harden user-interaction paths (UI:R) via procedural controls and change management for QIOMON-related operations.
   • Monitor for crashes, unexpected corruption, and anomalous input directed at QIOMON; correlate with the detections above.
   • Apply network segmentation and host-based monitoring on NonStop nodes hosting QIOMON.

2. Patch / upgrade steps:

   • No patch reference is available from any tracked source. Monitor HPE NonStop security advisories and HPE support channels for the official fix for CVE-2026-76661.
   • When a fix is published, validate it in a non-production environment, then schedule and apply promptly per change control.

3. Long-term hardening:

   • Keep NonStop environments and all components current with vendor advisories.
   • Implement a formal CVE monitoring and patch management process for NonStop subsystems.
   • Apply defense-in-depth input validation hygiene to custom components interacting with QIOMON.
   • Maintain baseline integrity and availability monitoring to detect memory corruption and crashes early.

References

• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-76661
• FIRST EPSS (not yet scored): https://www.first.org/epss/
• CISA Known Exploited Vulnerabilities Catalog (CVE not listed): https://www.cisa.gov/known-exploited-vulnerabilities-catalog
• HPE Security Bulletin / Support Center (monitor for advisory): https://support.hpe.com/
• MITRE ATT&CK T1190 — Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/

No public exploit, PoC, or in-the-wild activity has been observed for CVE-2026-76661. No threat actor campaign is currently associated. The CVE is not present in CISA KEV, and no EPSS score is available.