CVE-2026-91103: HP Linux Imaging and Printing RCE Vulnerability

CVE-2026-91103 Overview

HP disclosed CVE-2026-91103, an integer underflow vulnerability [CWE-191] affecting HP Linux Imaging and Printing (HPLIP) software. The flaw is part of a set of externally reported issues in HPLIP components that could enable remote code execution, privilege escalation, denial of service, information disclosure, or unauthorized file modification depending on the affected component. This specific entry describes a physically adjacent, low-complexity condition that primarily impacts availability. HP has issued remediation guidance through its security bulletin.

Critical Impact
Successful exploitation can trigger a denial-of-service condition against the HPLIP-managed printing subsystem, disrupting print and scan services on affected Linux hosts.

Affected Products

HP Linux Imaging and Printing (HPLIP) software components
Linux systems running vulnerable HPLIP releases
HP printing and multifunction devices managed through HPLIP

Discovery Timeline

2026-09-16 - CVE-2026-91103 published to the National Vulnerability Database (NVD)
2026-09-17 - Last updated in NVD database

Technical Details for CVE-2026-91103

Vulnerability Analysis

CVE-2026-91103 is classified as an integer underflow [CWE-191]. The condition occurs when arithmetic on an unsigned integer value drops below zero, wrapping to a very large positive value. In HPLIP, such wrap-around behavior can misdirect subsequent buffer or loop calculations and destabilize the affected process.

The attack vector is physical, meaning an attacker requires physical or physically adjacent access to the target device or interface to trigger the flawed code path. No authentication and no user interaction are required once access is established. The impact is limited to availability, with confidentiality and integrity unaffected in this entry.

HP describes the broader HPLIP advisory as covering multiple externally reported issues, some of which could enable remote code execution, privilege escalation, information disclosure, or unauthorized file modification. Administrators should treat CVE-2026-91103 as one component of that bulletin rather than an isolated issue.

Root Cause

The root cause is improper validation of integer arithmetic within an HPLIP component. When a computation subtracts from a value smaller than expected, the result underflows and corrupts downstream size or index calculations. This leads to abnormal termination or resource exhaustion in the affected process.

Attack Vector

Exploitation requires physical proximity or access to a locally connected interface exposed by the HPLIP stack, such as a USB or direct device channel. An attacker submits crafted input that reaches the vulnerable arithmetic operation, forcing the underflow and causing the process to fail. The vulnerability cannot be triggered remotely across a network based on the published vector.

No public proof-of-concept exploit, ExploitDB entry, or CISA KEV listing exists for CVE-2026-91103 at the time of publication. See the HP Security Bulletin for vendor-published technical details.

Detection Methods for CVE-2026-91103

Indicators of Compromise

Unexpected crashes or restarts of HPLIP daemons such as hpssd, hp-plugin, or related helper processes
Kernel or systemd journal entries referencing segmentation faults in HPLIP binaries
Sudden loss of print or scan availability tied to a locally attached HP device

Detection Strategies

Inventory Linux endpoints for installed HPLIP packages and compare versions against the fixed release identified in the HP bulletin
Monitor /var/log/syslog, journalctl, and application logs for repeated HPLIP process termination events
Correlate USB device connection events with HPLIP service failures to identify potentially malicious physical inputs

Monitoring Recommendations

Enable centralized logging for HPLIP services and forward events to a SIEM for baseline and anomaly analysis
Track process crash telemetry on Linux print servers, especially systems with directly attached HP hardware
Alert on new or unrecognized USB peripheral enumeration on servers hosting HPLIP

How to Mitigate CVE-2026-91103

Immediate Actions Required

Review the HP Security Bulletin and identify affected HPLIP versions in the environment
Apply the vendor-provided HPLIP update to all Linux systems that manage HP printers or scanners
Restrict physical and USB access to Linux hosts running HPLIP, particularly shared print servers

Patch Information

HP has published remediation guidance in security bulletin hpsbpi04151. Administrators should upgrade HPLIP to the fixed release specified by HP for their distribution. Consult the vendor advisory for version mappings and package sources.

Workarounds

Disable or remove HPLIP on systems that do not require HP printing or scanning functionality
Enforce USB port controls and physical access policies on Linux print servers
Limit local user accounts and group memberships that can interact with HPLIP device nodes and sockets

bash

# Verify installed HPLIP version on Debian/Ubuntu
dpkg -l | grep -i hplip

# Verify installed HPLIP version on RHEL/Fedora
rpm -qa | grep -i hplip

# Remove HPLIP if not required
sudo apt-get remove --purge hplip hplip-data   # Debian/Ubuntu
sudo dnf remove hplip hplip-common             # RHEL/Fedora