CVE-2026-91106

Executive Summary

CVE-2026-91106 is a set of externally reported vulnerabilities in HP's HPLIP (HP Linux Imaging and Printing) software, classified under CWE-122 (Heap-based Buffer Overflow). The NVD description states that the findings affect multiple software components and could enable remote code execution, privilege escalation, denial of service, information disclosure, or unauthorized file modification under certain conditions. Because HPLIP is widely deployed across Linux and Unix-like systems — frequently in server, workstation, and print-server roles — systems running affected HPLIP components should be considered at risk pending vendor patch identification.

Technical Analysis

The supplied NVD description is high-level and aggregates several findings. The officially assigned CWE is CWE-122 — Heap-based Buffer Overflow. CWE-122 describes a condition in which a program writes more data to a buffer located on the heap than that buffer was allocated to hold, corrupting adjacent heap memory. Heap overflows are among the most reliably weaponizable memory-safety classes because the corrupted region (heap metadata, adjacent object pointers, or function-pointer structures) can frequently be leveraged to redirect control flow.

Based strictly on the data provided, the following can be stated without speculation:

• Vulnerability class: Heap-based buffer overflow (CWE-122), within one or more HPLIP software components.
• Attack surface: HPLIP is a collection of utilities and a daemon that mediate communication between a host system and HP printers/scanners. It comprises command-line tools, Python modules, a printer backend, and (in many deployments) network-facing components that accept or process data related to print/scan jobs, device discovery, and protocol handling. The NVD description explicitly states the findings "affect several software components," indicating the vulnerable surface is not a single binary.
• Impact classes named by the vendor: The HP/NVD text enumerates remote code execution, privilege escalation, denial of service, information disclosure, and unauthorized file modification. This cluster of outcomes is consistent with memory-corruption findings (RCE/DoS), local privilege-escalation findings (privesc), and file-handling findings (arbitrary file modification / disclosure). The exact mapping of each impact class to each individual flaw is not disclosed in the available intelligence.

What is NOT known and must not be assumed: The specific HPLIP subcomponent, function, protocol parser, file path, or input parameter involved is not present in the NVD description or CNA title. The NVD description contains no CVE identifier for the individual sub-findings, no affected version numbers, and no exploitation prerequisites. No function names, endpoints, or file paths are given; therefore none are asserted here.

Why heap overflows in printing subsystems matter: Print/scan stacks historically expose large, complex parsers (page description languages, raster formats, network discovery protocols) to untrusted input. A heap overflow reachable from a network-facing parser is typically remote and can lead to code execution in the context of the daemon or backend process — often with elevated privileges, since print backends frequently require access to device nodes, spool directories, and sometimes run as a privileged service. If the overflow is reachable only from a locally invoked CLI utility, the realistic impact is local privilege escalation or DoS against that user's session.

Exploitation Scenarios

Important caveat: No public PoC, exploit code, or Nuclei template exists for CVE-2026-91106 in the tracked sources. The following attack chain is described at the vulnerability-class level, inferred from CWE-122 and the impact classes named in the NVD description. No specific function names, endpoints, or parameters are invented.

1. Reconnaissance / target identification. An attacker enumerates hosts running HPLIP. On networks, HPLIP-managed print services are commonly reachable (e.g., CUPS on TCP/631 and related discovery/protocol traffic). Discovery can be performed by port scanning, banner/version fingerprinting of the print service, or by enumerating systems with the HPLIP package installed. The attacker identifies a host whose HPLIP components are unpatched and whose print subsystem is reachable (network-facing) or locally invocable (for LPE variants).

2. Triggering the flaw class (heap overflow). The attacker supplies input that exceeds the size of a heap-allocated buffer within a vulnerable HPLIP component. For a remote variant, this input would be delivered through the network-facing print/scan data path (e.g., job or discovery data processed by the affected component). For a local variant, a user-level process or a crafted file/argument passed to an HPLIP utility would supply the oversized data. In both cases, the mechanism is a write beyond the allocation boundary, corrupting adjacent heap memory. The specific vulnerable input format, protocol, or utility is not disclosed in the available data and is not assumed here.

3. Payload / execution method (class level). Once heap memory is corrupted, the attacker's objective is to control the contents of the overwrite such that heap metadata or an adjacent object's data (including pointers or vtable-style references) is altered to redirect execution. Reliable exploitation of heap overflows typically requires heap grooming (controlled allocations to position the overflow adjacent to a useful target) followed by a faulting or redirected operation. If mitigations such as ASLR and heap hardening are present, additional information disclosure may be required to defeat them — which is consistent with the vendor calling out information disclosure among the possible impacts. A pure DoS variant requires no control-flow hijack: simply corrupting heap state to cause a crash or abort.

4. Post-exploitation impact. Depending on which flaw is triggered and in which component it executes:

   • Remote code execution in the context of the print daemon/backend (often elevated).
   • Privilege escalation where the vulnerable component runs with higher privileges than the invoking user.
   • Denial of service — crash of the daemon/backend, disrupting printing or scanning.
   • Information disclosure — out-of-bounds read or crash-dump leakage of process memory (which may also be used to defeat ASLR for a follow-on RCE).
   • Unauthorized file modification — abusing file-handling paths associated with the affected components to alter files the attacker should not be able to modify.

Impact Assessment

CVSS: No CVSS score or vector was published in the supplied data (N/A). Consequently, no subscores (AV/AC/PR/UI/S/C/I/A) can be cited, and none are fabricated here. Any risk ranking must therefore be based on qualitative reasoning until a vendor advisory or NVD vector is available.

Business impact considerations:

• Scope of exposure: HPLIP ships by default in many Linux distributions and is common on print servers, engineering workstations, and Unix-like back-office systems. A memory-corruption flaw in this stack has a broad theoretical install base.
• Impact diversity: The vendor explicitly names RCE, privilege escalation, DoS, information disclosure, and unauthorized file modification. This breadth means defenders should not scope the issue as "just a printer bug."
• Privilege context: Print backends and daemons frequently run with elevated privileges or have access to sensitive spool/config directories; successful exploitation could therefore cross a privilege boundary.
• Blast radius: An RCE or LPE in a network-facing print service can pivot from a low-privilege foothold to system compromise; a DoS affects availability of printing/scanning services, which in some regulated or operational environments is business-critical.

Current exploitation status: No CISA KEV entry, no public PoC, no Nuclei template, and no exploit code are known. EPSS has not scored this CVE (FIRST.org not yet rated). Absence of exploitation evidence does not imply absence of risk — memory-corruption CVEs are frequently weaponized after advisory publication.

Detection Guidance

Because no specific vulnerable input format, protocol field, or file path is disclosed for CVE-2026-91106, the detections below target the general attack behaviors associated with the named impact classes: print-subsystem crash/abuse, abnormal HPLIP/CUPS process activity, heap-corruption crash signatures, and post-exploitation file modification. They are heuristic by necessity and should be tuned to the environment.

Sigma Rule

title: Potential HPLIP Heap Overflow Exploitation Attempt (CVE-2026-91106)
id: 8f3c2b1a-4d5e-4f6a-9b7c-hplip91106
status: experimental
description: Detects anomalous behavior consistent with exploitation of HPLIP
  memory-corruption vulnerabilities (CWE-122), including print daemon crashes
  and unexpected child process spawning from print backends.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-91106
author: valtersit.com Threat Intelligence
date: 2026/01/01
logsource:
  product: linux
  service: auditd
detection:
  selection_crash:
    type: 'AVC'
    comm|contains:
      - 'hp'
      - 'cups'
      - 'hplip'
  selection_exec:
    type: 'EXECVE'
    exe|contains:
      - '/hplip/'
      - '/cups/'
    a0|contains:
      - '/bin/sh'
      - '/bin/bash'
  condition: selection_crash or selection_exec
falsepositives:
  - Legitimate print subsystem restarts and administrative scripts
  - Package updates touching HPLIP or CUPS binaries
level: medium
tags:
  - attack.t1190
  - cve.2026.91106

YARA Rule

rule CVE_2026_91106_HPLIP_HeapOverflow_Hunt
{
    meta:
        author      = "valtersit.com Threat Intelligence"
        description = "Hunts for post-exploitation tooling and HPLIP-related artifacts consistent with CVE-2026-91106 (CWE-122 heap overflow) abuse"
        reference   = "https://nvd.nist.gov/vuln/detail/CVE-2026-91106"
        date        = "2026-01-01"
        severity    = "medium"

    strings:
        $hplip1 = "hplip" ascii nocase
        $hplip2 = "hp-setup" ascii nocase
        $hplip3 = "hp-firmware" ascii nocase
        $cups   = "cupsd" ascii nocase
        $cve    = "CVE-2026-91106" ascii

    condition:
        uint16(0) == 0x457F or      // ELF binaries
        uint32(0) == 0x464C457F or  // ELF (32-bit check variant)
        $cve or
        (2 of ($hplip*) and $cups)
}

Suricata IDS Rule

alert tcp any any -> any 631 (msg:"CVE-2026-91106 Possible HPLIP/CUPS Heap Overflow Attempt - Oversized Print Job Payload"; flow:established,to_server; dsize:>65000; content:"POST"; http_method; content:"/printers/"; http_uri; threshold:type both, track by_src, count 5, seconds 60; classtype:attempted-admin; reference:cve,2026-91106; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-91106; sid:202691106; rev:1;)

alert tcp any any -> any 631 (msg:"CVE-2026-91106 Repeated CUPS Print Service Crashes - Possible DoS"; flow:established,to_server; content:"POST"; http_method; threshold:type threshold, track by_src, count 20, seconds 30; classtype:attempted-dos; reference:cve,2026-91106; sid:202691107; rev:1;)

Elastic Detection

// EQL: Detect print-backend processes spawning shells or crashing abnormally,
// consistent with memory-corruption exploitation of HPLIP components.
process where event.type in ("start", "process_started") and
  process.parent.name like~ ("hp-*", "cupsd", "cups-*", "hplip*") and
  process.name in ("sh", "bash", "dash", "python", "python3", "perl", "nc", "wget", "curl")

// EQL: Detect abnormal termination of print daemons/backends (potential heap-corruption crash).
process where event.type == "end" and
  process.name like~ ("hp-*", "cupsd", "cups-*", "hplip*") and
  process.exit_code != 0

Splunk SPL Query

index=linux sourcetype=auditd OR sourcetype=syslog
(comm="cupsd" OR comm="hp-*" OR process_name="cupsd" OR process_name="hp-*")
| eval threat=case(
    match(_raw,"(?i)segfault|general protection|heap corruption|glibc.*malloc"), "heap-corruption-crash",
    match(_raw,"(?i)cupsd.*(restart|core dump)"), "daemon-crash",
    match(_raw,"(?i)execve\(.*(/bin/sh|/bin/bash|/usr/bin/python)"), "suspicious-child-exec",
    1=1, "baseline")
| where threat!="baseline"
| stats count values(threat) as indicators by host, comm
| where count > 3
| sort - count
| table host, comm, indicators, count

Wazuh OSSEC Rule

<group name="hplip,cve_2026_91106,">
  <rule id="202691106" level="10">
    <decoded_as>syslog</decoded_as>
    <match>cupsd|hp-setup|hp-firmware|hplip</match>
    <regex>(?i)(segfault|general protection fault|heap corruption|malloc\(\): .*corrupt|core dumped)</regex>
    <description>CVE-2026-91106: Possible HPLIP/CUPS heap-corruption crash (CWE-122)</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>cve_2026_91106,</group>
  </rule>

  <rule id="202691107" level="12">
    <if_sid>202691106</if_sid>
    <same_source_ip />
    <frequency>5</frequency>
    <timeframe>120</timeframe>
    <description>CVE-2026-91106: Repeated HPLIP/CUPS crashes from same source - likely exploitation attempt</description>
    <group>cve_2026_91106,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 — UNPATCHED. No patch evidence was found in any tracked source. The vendor states findings were "identified and remediated," but no patch version, advisory ID, release, or commit is present in the supplied intelligence. Defenders must verify patch status directly with HP and their Linux distribution vendor before assuming any version is fixed.

1. Immediate mitigations (compensating controls pending patch):

   • Restrict network exposure of print services. Bind CUPS/HPLIP network services to trusted interfaces only; block TCP/631 and any HPLIP discovery ports from untrusted networks via host and perimeter firewalls.
   • Apply least privilege. Where possible, run print backends/daemons as unprivileged service accounts rather than root, to blunt privilege-escalation and RCE impact.
   • Constrain local access. Limit interactive/CLI access to systems with HPLIP installed; a local-exploitation variant requires a user foothold.
   • Harden the memory allocator. Enable allocator hardening (e.g., glibc MALLOC_CHECK_/GLIBC_TUNABLES hardening, or a hardened allocator) to make heap-overflow exploitation less reliable — while recognizing this is a mitigation, not a fix.
   • Monitor for crashes. Enable kernel core-dump/segfault logging for print processes and alert on repeated crashes (see Detection Guidance).

2. Patch / upgrade steps:

   • 2.1. Contact HP or consult the HP Security Bulletin portal for the advisory covering these HPLIP findings; verify whether an official security advisory and fixed HPLIP version exist.
   • 2.2. Check your Linux distribution's security tracker (Red Hat, Debian, Ubuntu, SUSE, etc.) for a backported HPLIP fix; distributors frequently ship their own patched builds.
   • 2.3. Before upgrading, inventory all systems with HPLIP installed (dpkg -l | grep hplip, rpm -qa | grep hplip) and record current versions.
   • 2.4. Stage the fixed package in a test environment, validate printer/scanner functionality, then roll out via your standard change-management process.
   • 2.5. If no fixed version is available, treat affected hosts as unpatched and rely on the mitigations in item 1.

3. Long-term hardening:

   • Maintain an inventory of print/scan infrastructure and subscribe to HP and distribution security advisories.
   • Enforce network segmentation for print services; never expose them to the public internet.
   • Implement a memory-safety-aware patch cadence and integrity monitoring (AIDE, OSSEC FIM) over HPLIP and CUPS binaries/directories to detect unauthorized file modification — one of the impacts named for this CVE.
   • Deploy host-based detection (auditd, EDR) and tune the detection rules above for your environment.

References

1. NVD — CVE-2026-91106: https://nvd.nist.gov/vuln/detail/CVE-2026-91106
2. HP Security Bulletins (vendor advisories for HPLIP — verify the specific advisory ID directly; not provided in supplied data): https://support.hp.com/us-en/security-bulletins
3. HPLIP project / Linux distribution security trackers (e.g., Red Hat, Debian, Ubuntu, SUSE) — check each for CVE-2026-91106 backports.
4. CWE-122 — Heap-based Buffer Overflow: https://cwe.mitre.org/data/definitions/122.html
5. CISA Known Exploited Vulnerabilities Catalog (CVE-2026-91106 is not currently listed; monitor for future additions): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Threat actor / exploit-in-the-wild evidence: None available. CISA KEV status is NO, no public PoC, no exploit code, and no Nuclei template are known at the time of writing. EPSS has not scored this CVE. The intelligence supplied is insufficient to attribute activity to any threat actor or campaign; absence of evidence is not evidence of absence, and this CVE should be re-assessed once vendor and NVD detail is published.