CVE-2026-91105

Executive Summary

CVE-2026-91105 is a heap-based buffer overflow (CWE-122) class vulnerability affecting HPLIP, HP's Linux Imaging and Printing software. HP reported that multiple externally reported flaws — including this one — may allow remote code execution, privilege escalation, denial of service, information disclosure, or unauthorized file modification under certain conditions. Because no CVSS score, affected version range, or patch reference has been published by NVD or any tracked patch source, defenders must treat all HPLIP deployments as potentially exposed until HP releases version-specific remediation details.

Technical Analysis

CWE-122 (Heap-based Buffer Overflow) occurs when a program writes more data to a heap-allocated buffer than the buffer can hold. Heap allocations are dynamically sized at runtime, so an overflow corrupts adjacent heap metadata, function pointers, or object structures, which an attacker can often leverage to redirect control flow and achieve code execution or to cause memory corruption that crashes the process (denial of service).

Per the NVD description, this flaw resides "within HPLIP" and "affect[s] several software components." The description confirms HP has "identified and remediated multiple externally reported vulnerabilities" that "could potentially enable remote code execution, privilege escalation, denial of service, information disclosure, or unauthorized file modification under certain conditions."

Important accuracy note: The NVD description and CNA title provided do not disclose specific function names, file paths, endpoints, or parameter names for CVE-2026-91105. No public PoC, Nuclei template, or exploit code is available. Accordingly, this report describes the vulnerability at the class level and does not invent implementation specifics. The specific overflow location, trigger input, and reachable attack vector within HPLIP remain unconfirmed in open sources.

HPLIP is commonly deployed as a suite of daemons and utilities that handle print job submission, device discovery, and network communication with HP printers and multifunction devices. Historically, the relevant attack surface for a heap overflow in this class of software is one that 1) parses externally supplied data (network packets, print job data, PDL/PostScript streams, device responses, or configuration files) and 2) processes it with insufficient bounds checking on a heap buffer. However, because the advisory does not name the vulnerable component, no specific parser, endpoint, or protocol can be asserted with confidence for this CVE.

Patch confidence: 0/4 (UNPATCHED). No patch source, fixed-version reference, or vendor fix identifier was returned by any tracked source. The phrase "remote code execution, privilege escalation, denial of service, information disclosure, or unauthorized file modification" is broad, indicating HP's advisory aggregates multiple distinct issues; CVE-2026-91105 specifically maps to the heap overflow (CWE-122).

Confidence: LOW. The class (heap overflow) is well-supported by the CWE mapping. All implementation-level specifics are unavailable.

Exploitation Scenarios

Note: No public PoC is available; the attack chain below is inferred from the vulnerability class (CWE-122) and the CNA's advisory language. No specific HPLIP function names, endpoints, or file paths are asserted because the source data does not provide them.

1. Reconnaissance / target identification. An attacker identifies reachable HPLIP installations on the network. Candidate discovery surfaces include listening print/management ports (historically port 631 and related print/IPP services) and HPLIP daemons interacting with printers on the LAN. Shodan-style enumeration of exposed print service banners narrows the target set.

2. Triggering the heap overflow. The attacker delivers input to the vulnerable HPLIP component that is parsed into a heap-allocated buffer without adequate bounds enforcement. Because the advisory describes the issue as potentially reachable with remote impact ("remote code execution... under certain conditions"), the trigger is presumed to be attacker-controllable data reaching the flawed parser. The exact input channel (e.g., a crafted print job, malformed response, or configuration value) is not specified in the available data. Deterministic class-level condition: allocation size is computed independently of the actual data length, and the subsequent copy/write exceeds the allocation.

3. Execution / effect at the class level. Overflowing the heap buffer corrupts adjacent heap structures. Where function pointers or object vtable-style structures are adjacent, an attacker may redirect control flow toward attacker-influenced memory, yielding code execution in the context of the HPLIP process (which may be a privileged daemon, enabling privilege escalation). Where influence is insufficient for control-flow hijack, the corruption still results in a crash — a denial-of-service condition. Because HP's advisory also lists "information disclosure" and "unauthorized file modification," some aggregated issues may allow reading or altering files without full code execution.

4. Post-exploitation impact. Depending on the privileges of the HPLIP process and the degree of control achieved: arbitrary code execution, privilege escalation on the host, service/print subsystem outage (DoS), disclosure of print job contents or system files, or modification of files on the host filesystem.

Impact Assessment

The potential impact spans the full CIA triad, per the CNA advisory:

• Confidentiality: Information disclosure is explicitly cited — print job contents, credentials embedded in configuration, or system files may be exposed.
• Integrity: Unauthorized file modification and remote code execution are cited, implying an attacker could alter files or execute arbitrary commands.
• Availability: Denial of service is cited — heap corruption reliably crashes a process, taking print services offline.

Blast radius: All hosts running an affected HPLIP build are in scope. HPLIP is frequently installed on Linux workstations, servers acting as print servers, and systems configured for network printing. If the vulnerable component runs as a privileged daemon, successful exploitation can yield host-level privilege escalation.

CVSS: No CVSS score or vector has been published by NVD for this CVE. This report does not assign a score. Qualitatively, a heap overflow reachable by attacker-supplied input, with the potential for remote code execution and privilege escalation, would typically warrant a High to Critical rating — but this is a qualitative assessment, not an official score, and must not be represented as a CVSS value.

EPSS: Not yet scored by FIRST.org. No EPSS value is available or fabricated here.

CISA KEV: Not listed.

Exploit maturity: No public PoC, no Nuclei template, no exploit code, no known in-the-wild exploitation reported. Detection should focus on anomalous input/crash patterns rather than known signatures.

Detection Guidance

Sigma Rule

title: Possible HPLIP Heap Overflow Exploitation Attempt (CVE-2026-91105)
id: 9e3b7a10-1f42-4c8a-b6d5-2a7c91105000
status: experimental
description: Detects crashes or abnormal terminations of HPLIP-related processes potentially indicative of heap corruption (CWE-122) exploitation.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-91105
author: Valters IT Threat Intelligence
date: 2026-01-01
logsource:
  category: process_creation
  product: linux
detection:
  selection_hplip:
    Image|endswith:
      - '/hp-'
      - '/hplip'
      - '/hpijs'
      - '/hpcups'
  selection_fault:
    CommandLine|contains:
      - 'heap'
      - 'malloc'
  condition: selection_hplip and not selection_fault
falsepositives:
  - Legitimate printer troubleshooting
level: medium
tags:
  - attack.t1190
  - cwe.122

YARA Rule

rule CVE_2026_91105_HPLIP_HeapOverflow_Artifacts
{
    meta:
        description = "Heuristic detection of heap-overflow exploitation artifacts targeting HPLIP (CVE-2026-91105)"
        author = "Valters IT Threat Intelligence"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-91105"
        cwe = "CWE-122"
        date = "2026-01-01"

    strings:
        $hplip_1 = "HPLIP" ascii wide nocase
        $hplip_2 = "hp-print" ascii wide nocase
        $overflow_1 = "heap-buffer-overflow" ascii nocase
        $overflow_2 = "malloc(): corrupted" ascii nocase
        $overflow_3 = "glibc detected" ascii nocase

    condition:
        uint32(0) == 0x464c457f and
        (1 of ($hplip_*)) and
        (1 of ($overflow_*))
}

Suricata IDS Rule

alert tcp $EXTERNAL_NET any -> $HOME_NET [631,9100] (msg:"Possible HPLIP Heap Overflow Exploitation Attempt (CVE-2026-91105)"; flow:established,to_server; content:"|00 00 00 00|"; depth:4; threshold:type both, track by_src, count 20, seconds 60; classtype:attempted-admin; sid:9110501; rev:1; metadata:reference nvd,cve 2026-91105; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-91105;)

Elastic Detection

sequence by host.name
  [process where process.parent.name : "hplip*"]
  [file where event.action : "creation" and process.name : "hp-*"]

Splunk SPL Query

index=linux sourcetype=syslog OR sourcetype=linux_secure
("hp-" OR hplip OR hpijs OR hpcups OR cups)
| search ("segfault" OR "SIGSEGV" OR "glibc detected" OR "heap" OR "malloc(): corrupted" OR "corrupted top size" OR "Aborted")
| stats count values(message) as messages by host, process, source
| where count > 0

Wazuh OSSEC Rule

<group name="hplip,CVE-2026-91105,">
  <rule id="911050" level="10">
    <decoded_as>syslog</decoded_as>
    <match>hplip|hp-print|hpijs|hpcups</match>
    <regex>heap|malloc\(\): corrupted|glibc detected|segfault|SIGSEGV</regex>
    <description>Possible HPLIP heap overflow exploitation attempt (CVE-2026-91105)</description>
    <mitre>
      <id>T1190</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source). No fixed HPLIP version, vendor advisory reference, or workaround has been published in the data available. The steps below are defensive best practices for an unpatched heap-overflow in a print subsystem; they are not vendor-confirmed fixes.

1. Immediate mitigations

• Remove HPLIP/print-related services from untrusted network exposure: restrict print and management ports (historically 631 and 9100) to trusted management networks via firewall/ACL rules.
• Disable printing subsystems and unnecessary print daemons on servers and workstations that do not require them.
• Where HPLIP must run, minimize the privileges of the process; do not run print daemons as root unnecessarily.
• Segment printing infrastructure from general user networks.
• Monitor for process crashes of HPLIP binaries and capture core dumps for forensic review.
• Remove default credentials on printer/management interfaces and require authentication for any exposed print service.

2. Patch / upgrade steps

• Track HP's HPLIP security advisories and the NVD entry for CVE-2026-91105 for a fixed version.
• When a patched HPLIP release is published, upgrade using your distribution's package manager or HP's official HPLIP release channel.
• Verify package provenance and signatures before deployment.
• Until a fix is available, treat affected hosts as unpatched and prioritize mitigation by exposure.

3. Long-term hardening

• Maintain an inventory of HPLIP versions across all Linux endpoints; classify which run network-exposed print services.
• Implement egress and lateral-movement restrictions from print servers.
• Deploy memory-corruption-oriented mitigations (ASLR, hardened allocators, stack/heap protections via distro hardening).
• Subscribe to HP security bulletins and the NVD feed for HPLIP to detect the patch release promptly.
• Consider containerizing or sandboxing print services to contain exploitation impact.

References

1. NVD — CVE-2026-91105: https://nvd.nist.gov/vuln/detail/CVE-2026-91105
2. HP Security Bulletins portal (HPLIP advisories): https://support.hp.com/us-en/security-bulletins
3. CWE-122 (Heap-based Buffer Overflow): https://cwe.mitre.org/data/definitions/122.html
4. MITRE ATT&CK T1190 — Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/
5. HPLIP project site (vendor upstream): https://developers.hp.com/hp-linux-imaging-and-printing

Threat actor / exploit-in-the-wild note: No threat actor campaigns and no exploit-in-the-wild evidence for CVE-2026-91105 were identified in the provided data. CISA KEV status is NO, and no EPSS score, PoC, Nuclei template, or exploit code is available. This report intentionally does not assert attribution or active exploitation.