CVE-2026-76660

Executive Summary

CVE-2026-76660 is an out-of-bounds write vulnerability in HPE NonStop CIPSAM (the Common Internet Protocol Subsystem / subsystem-adjacent component referenced by that name in the advisory) that corrupts adjacent buffer memory. It carries a CVSS 3.1 base score of 8.7 (High), reflecting a local attack vector, low attack complexity, low privileges required, and a scope change, with High impact to integrity and availability and Low impact to confidentiality. No public proof-of-concept, exploit code, or Nuclei template exists, no patch evidence is available from any tracked source, and the CVE has not been added to CISA KEV and has no EPSS score published by FIRST.org as of this writing. Organizations running HPE NonStop systems with CIPSAM deployed should treat this as an unpatched, locally reachable memory-corruption issue requiring compensating controls until a vendor fix is released.

Technical Analysis

The vulnerability class here is a memory-safety defect: an out-of-bounds write. Per the available NVD description, the flaw "allows an out-of-bounds write that can corrupt buffer data" within HPE NonStop CIPSAM. That description is intentionally sparse — it does not disclose the specific routine, parameter, packet field, or input path that drives the write, and this report will not fabricate those details.

What can be stated with confidence from the CVSS vector:

• Attack vector: Local (AV:L). The attacker must already be able to execute code or issue commands in a context on the target system that can reach the vulnerable CIPSAM code path. This is not a remote, unauthenticated network exploit.
• Attack complexity: Low (AC:L). No race condition, no exotic memory layout grooming, and no highly specialized preconditions are implied — once the vulnerable code path is reachable, reliable triggering is expected.
• Privileges required: Low (PR:L). A low-privileged local user or process is sufficient. Administrative or elevated rights are not a prerequisite to trigger the flaw.
• User interaction: None (UI:N). No victim must open a file, click a link, or confirm an action.
• Scope: Changed (S:C). Exploitation can affect resources beyond the vulnerable component's original security authority — i.e., corruption in CIPSAM can impact other components, processes, or subsystems on the host.

The CWE assignment is CWE-20 (Improper Input Validation). This is consistent with the mechanism: input supplied to CIPSAM is not adequately validated (most plausibly a length, size, or boundary check that is missing or incorrect), and the subsequent write operation indexes or copies past the end of the intended destination buffer, overwriting adjacent memory. The NVD description stops at "corrupt buffer data"; it does not state which fields or structures are adjacent to the buffer, what the maximum overrun is, whether the write is attacker-controlled in content, or whether the corruption is deterministic in size.

Attack surface. Because the vector is local, the practical attack surface is any local interface, command, utility, or inter-process path that feeds data into CIPSAM's parsing or processing logic. CIPSAM's role in the NonStop environment places it in the data path for protocol handling, meaning the vulnerable routine is reached through normal subsystem operations as well as through any local caller that can submit input to it. The scope change indicates the corrupted buffer does not remain contained within the CIPSAM process boundary — corruption of shared or adjacent structures can cascade into other processes or the operating environment.

Code-level explanation. Not available. The advisory provides no function names, no file paths, no parameter names, no offsets, and no encapsulation of the vulnerable copy/index operation. Any named function or field presented as fact in a report on this CVE would be fabricated. The accurate summary is: an input-validation failure permits a write operation to exceed a buffer boundary, corrupting adjacent memory in a locally reachable component, with potential cross-boundary (scope-changed) effects.

Why the score is High despite Low confidentiality impact. Integrity and Availability are both rated High. An out-of-bounds write is a classic memory-corruption primitive: it can overwrite control or data structures to alter program state (integrity), and it can crash or destabilize the component and anything sharing the corrupted region (availability). Confidentiality is only Low because the write primitive as described does not inherently read and exfiltrate data — though a sophisticated attacker may chain the corruption into information disclosure or code execution, which is precisely why the scope change matters. In practice, memory-corruption primitives of this class are frequently the first stage of a privilege-escalation or code-execution chain.

Exploitation Scenarios

No public PoC, exploit code, or Nuclei template is available for CVE-2026-76660. The following chain is described at the vulnerability-class level and is inferred strictly from the NVD description (out-of-bounds write in HPE NonStop CIPSAM, local vector, low privileges, scope change) and the CVSS vector. It does not assert specific function names, endpoints, parameters, or code constructs, because none are disclosed.

1. Reconnaissance / target identification. The attacker gains access to a NonStop host at low privilege — for example, an unprivileged account, a compromised low-privilege service, or a local process context. The attacker enumerates whether CIPSAM is present and reachable from that context. Because the vector is local, no remote probing or network scanning is required; the reconnaissance is on-host. An attacker with any foothold on a NonStop system can determine the presence of the subsystem through normal local enumeration.

2. Triggering the flaw class. The attacker identifies a local input path that delivers data into CIPSAM's processing logic — a command, utility, or inter-process interface that reaches the routine containing the missing/inadequate validation. The attacker constructs input that violates the expected bounds (for example, a length or size value that exceeds what the destination buffer can hold). CWE-20 (Improper Input Validation) tells us the check that should have rejected the oversized or malformed input is absent or insufficient. When the input is processed, the write operation exceeds the buffer boundary and overwrites adjacent memory.

3. Payload/execution method. At the vulnerability-class level, the attacker's objective with an out-of-bounds write is to place controlled bytes into memory that the program later uses — either to corrupt data structures to redirect control flow, to overwrite a function pointer or return address, or to corrupt state that other components subsequently trust. The NVD description does not state whether the write content is attacker-controlled, which is the key factor distinguishing a deterministic crash from a controllable corruption primitive. Access level required is low (PR:L); complexity is low (AC:L); no user interaction is needed (UI:N).

4. Post-exploitation impact. Because the scope is Changed (S:C), successful corruption is not contained to CIPSAM. The attacker can expect one or more of: process crash or denial of service (Availability: High), corruption of data or state used by CIPSAM or neighboring components (Integrity: High), and — if the corruption is shaped into a reliable primitive — escalation of privileges on the NonStop host or execution of attacker-chosen code in a higher-integrity context. Even the baseline outcome, a reliable local crash of a system component, is operationally serious on a NonStop platform where availability guarantees are the reason the platform is deployed.

Assessment. Exploitation is plausible for a motivated local attacker given low complexity and low privilege requirements, but no evidence of in-the-wild exploitation, no public tooling, and no KEV listing exist. The absence of a disclosed affected-version range means the population of vulnerable hosts cannot be precisely scoped from public data.

Impact Assessment

• Business impact. HPE NonStop systems underpin transaction processing, payments, and other high-availability workloads where downtime and data corruption carry direct financial and regulatory cost. A local memory-corruption flaw with High integrity and availability impact is a direct threat to both data trustworthiness and uptime. The scope change means a single corrupted process can degrade or destabilize resources beyond its own boundary, broadening operational blast radius.
• Affected systems. HPE NonStop deployments that include CIPSAM. Exact affected versions are not published in the available data, so asset owners must determine relevance from HPE documentation and their installed subsystem inventory rather than from a version boundary in this report.
• Blast radius and attacker profile. The local vector and low privilege requirement mean this is primarily a post-foothold escalation and disruption primitive rather than an initial-access vector. Relevant threat actors: malicious insiders, attackers who have already compromised a low-privilege account or service on the host, and red teams validating host-level hardening. It is not, on the disclosed information, remotely exploitable without a prior local foothold.
• CVSS interpretation. 8.7 High = AV:L / AC:L / PR:L / UI:N / S:C / C:L / I:H / A:H. The score is driven by low complexity, no user interaction, the scope change, and the High integrity and availability impact. Confidentiality is Low: no read/exfiltration primitive is described.
• Urgency factors. Patch confidence is 0/4 — no patch evidence from any tracked source — and no EPSS score has been published. Unpatched status raises the value of compensating controls and monitoring. Absence from CISA KEV and absence of public exploit code both argue against treating this as an immediate emergency, but the unpatched state and High score warrant prioritized inventory and hardening.

Detection Guidance

Because no exploit artifacts, function names, or network signatures are published for this CVE, the following rules are necessarily behavioral and deployment-specific. They target the observable consequences of an out-of-bounds write reachable via local input: crashes and abnormal terminations of CIPSAM-related processes, repeated abnormal exits, and unusual local invocation patterns against the subsystem. These rules should be tuned to the actual process and file names present on the target NonStop host; placeholders are marked as such and must not be treated as confirmed artifacts for this CVE.

Sigma Rule

title: Potential CIPSAM Out-of-Bounds Write - Abnormal Process Termination
id: 7c2f9a10-5b4e-4d21-9a77-3e0b1c6d7666
status: experimental
description: Detects abnormal termination or repeated crashes of HPE NonStop CIPSAM-related processes, which may indicate a local out-of-bounds write (CVE-2026-76660). Process names are placeholders and must be tuned to the target environment.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-76660
author: valtersit.com
date: 2026/01/01
tags:
  - attack.t1068
  - cve.2026.76660
logsource:
  category: process_creation
  product: linux
detection:
  selection:
    Image|endswith:
      - '/cipsam'
      - '/cipsam.exe'
    # tune to the actual listener/worker binary names on the NonStop host
  condition: selection
falsepositives:
  - Legitimate maintenance restarts of CIPSAM
  - Scheduled subsystem recycling
level: medium

YARA Rule

rule CVE_2026_76660_CIPSAM_OOB_Write_Artifact
{
    meta:
        description = "Placeholder artifact-detection rule for CVE-2026-76660 (HPE NonStop CIPSAM out-of-bounds write). No public exploit artifacts exist; strings below are generic and require environment-specific tuning."
        author = "valtersit.com"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-76660"
        date = "2026-01-01"
        severity = "high"

    strings:
        $s1 = "CIPSAM" ascii nocase
        $s2 = "buffer overflow" ascii nocase
        $s3 = "out-of-bounds" ascii nocase

    condition:
        uint16(0) == 0x5A4D and any of ($s*) or
        (filesize < 5MB and 2 of ($s*))
}

Suricata IDS Rule

alert tcp $HOME_NET any -> $HOME_NET any (msg:"CVE-2026-76660 - Potential HPE NonStop CIPSAM abuse traffic (tuning required, no published signature)"; flow:to_server,established; threshold:type both, track by_src, count 20, seconds 60; classtype:attempted-user; sid:90076660; rev:1; reference:cve,2026-76660; metadata:service unknown;)

Note: no network signature for this CVE is published. The rule above is a placeholder that fires on connection-rate anomalies to the locally exposed CIPSAM service port and must be tuned to a known-good listener port; it will not detect the vulnerability itself, only unusual access volume.

Elastic Detection

process where event.type == "end" and process.name like~ ("cipsam*") and
process.exit_code != 0

Additional EQL to correlate repeated abnormal exits of the same subsystem within a short window (tune index and time window):

sequence by host.name with maxspan=5m
  [process where event.type == "end" and process.name like~ ("cipsam*") and process.exit_code != 0]
  [process where event.type == "start" and process.name like~ ("cipsam*")]

Splunk SPL Query

index=main (sourcetype=syslog OR sourcetype=ossec OR sourcetype=edr:process)
(process_name IN ("cipsam","cipsam.exe") OR "CIPSAM")
(signal="SIGSEGV" OR signal="SIGABRT" OR "core dumped" OR "buffer" OR "out-of-bounds")
| stats count min(_time) as first_seen max(_time) as last_seen values(signal) as signals by host, process_name, user
| where count >= 3
| convert ctime(first_seen) ctime(last_seen)
| sort - count

Wazuh OSSEC Rule

<group name="hpe_nonstop,cve_2026_76660,">
  <rule id="100660" level="10">
    <decoded_as>json</decoded_as>
    <field name="process">cipsam</field>
    <match>segmentation fault|core dumped|abort|out-of-bounds|buffer</match>
    <description>CVE-2026-76660: Potential HPE NonStop CIPSAM out-of-bounds write - abnormal termination of CIPSAM process detected</description>
    <mitre>
      <id>T1068</id>
    </mitre>
    <group>cve_2026_76660,memory_corruption,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 — UNPATCHED. No patch evidence from any tracked source. No vendor fix, workaround, or affected-version range has been published in the data available for this CVE. The guidance below is compensating-control oriented.

1. Immediate mitigations

   • Restrict local access to NonStop hosts running CIPSAM to the minimum set of authenticated users and processes required for operations. Because the vector is local with low privilege required (PR:L), reducing the number of accounts and processes that can reach the vulnerable code path directly narrows the attack surface.
   • Enforce least privilege on service accounts and eliminate shared or generic low-privilege credentials that could serve as an attacker foothold.
   • Audit local input paths into CIPSAM: identify which utilities, commands, and inter-process interfaces can deliver data to the subsystem, and apply the strongest available access controls to each.
   • Increase monitoring for abnormal CIPSAM process terminations and core dumps (see detection rules above), and enable core-dump capture where feasible to support root-cause analysis.
   • Apply network segmentation and host-level controls so that a compromise of a low-privilege local account does not transitively expose other high-value NonStop subsystems (relevant given the Scope:Changed rating).

2. Patch/upgrade steps

   • Monitor HPE's official security bulletin and product support channels for a NonStop CIPSAM advisory addressing this CVE. No patch identifier or fixed version is available at this time; do not assume any specific release resolves it until HPE publishes the fix.
   • Track the NVD entry (https://nvd.nist.gov/vuln/detail/CVE-2026-76660) and subscribe to HPE security notifications. When a fixed version is published, validate it in a non-production environment and roll it out on an accelerated schedule for internet- or partner-facing transaction hosts.
   • Until a patch exists, document the exposure as an accepted, mitigated risk with an explicit review date.

3. Long-term hardening

   • Establish an inventory of HPE NonStop CIPSAM deployments and their versions so that, once a fixed version is identified, response can be scoped immediately.
   • Adopt a host-level least-privilege and strict service-account governance model, since local vector vulnerabilities are defeated primarily by limiting who can run code on the host at all.
   • Deploy memory-corruption and crash-telemetry detection at the host layer (EDR/OS-level) and feed it into the SOC for correlation, since memory-safety flaws are detectable chiefly through their crash and corruption artifacts.
   • Include local privilege-escalation scenarios in purple-team exercises against NonStop infrastructure, prioritizing the T1068 tactic path that this CVE represents.
   • Maintain an offline, tested recovery plan for CIPSAM-dependent services to preserve availability commitments in the event of a corruption-induced outage.

References

• NVD — CVE-2026-76660: https://nvd.nist.gov/vuln/detail/CVE-2026-76660
• MITRE ATT&CK — T1068, Exploitation for Privilege Escalation: https://attack.mitre.org/techniques/T1068/
• CWE-20 — Improper Input Validation: https://cwe.mitre.org/data/definitions/20.html
• FIRST.org EPSS — CVE-2026-76660 (no score currently published): https://api.first.org/data/v1/epss?cve=CVE-2026-76660
• CISA Known Exploited Vulnerabilities Catalog (CVE-2026-76660 not listed as of this report): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

No threat actor campaigns, exploit-in-the-wild evidence, public PoC, or HPE vendor advisory for CVE-2026-76660 were identified in the data available at the time of writing.