CVE-2026-91100 Overview
HP has disclosed multiple vulnerabilities in HP Linux Imaging and Printing (HPLIP) software. The flaws affect several software components and can lead to remote code execution, privilege escalation, denial of service, information disclosure, or unauthorized file modification under specific conditions. CVE-2026-91100 is categorized under [CWE-78] (Improper Neutralization of Special Elements used in an OS Command), indicating an OS command injection weakness within HPLIP components. The vulnerability requires local access and user interaction, but successful exploitation yields high integrity impact on the affected host.
Critical Impact
Local attackers can inject operating system commands through HPLIP components, potentially modifying files, escalating privileges, or executing arbitrary code on the host.
Affected Products
- HP Linux Imaging and Printing (HPLIP) software suite
- Linux distributions bundling vulnerable HPLIP components
- HP printer and multifunction device management utilities relying on HPLIP
Discovery Timeline
- 2026-09-16 - CVE-2026-91100 published to the National Vulnerability Database
- 2026-09-17 - Last updated in NVD database
Technical Details for CVE-2026-91100
Vulnerability Analysis
CVE-2026-91100 is an OS Command Injection vulnerability [CWE-78] within HPLIP. HPLIP provides printing, scanning, and device management support for HP devices on Linux systems. The affected components fail to properly neutralize special elements passed into commands executed by the operating system shell. An attacker with local access can supply crafted input that alters the intended command, causing the shell to execute attacker-controlled instructions.
HP describes several distinct issues in the same advisory. These issues can enable remote code execution, privilege escalation, denial of service, information disclosure, or unauthorized file modification. The high integrity impact indicates that successful exploitation can modify files or system state that the compromised process is authorized to change.
Root Cause
The root cause is improper input validation and sanitization before constructing operating system commands. When user-controlled data flows into a shell invocation without escaping or argument-array construction, metacharacters such as semicolons, backticks, or pipes break out of the intended argument context. This allows the shell to interpret injected content as additional commands.
Attack Vector
The attack vector is local and requires user interaction. An attacker typically triggers the vulnerable code path by inducing a user to interact with a crafted device, file, print job, or utility that HPLIP processes. Because HPLIP components frequently run with elevated permissions during device configuration, successful command injection can extend attacker control beyond the invoking user context. See the HP Security Bulletin for component-specific technical details.
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Stop Exploit AttemptsDetection Methods for CVE-2026-91100
Indicators of Compromise
- Unexpected child processes spawned by HPLIP binaries such as hp-* utilities, hplip daemons, or hpcups filters invoking shells like /bin/sh or /bin/bash.
- Shell metacharacters (;, |, `, $() present in device names, printer URIs, or CUPS job parameters passed to HPLIP components.
- Modification of files outside standard HPLIP working directories by HPLIP processes.
Detection Strategies
- Monitor process ancestry for HPLIP components executing shell interpreters or system utilities like wget, curl, nc, or bash that are not part of normal print workflows.
- Enable auditd rules on Linux hosts to log execve calls originating from HPLIP binaries and correlate with unusual argument patterns.
- Baseline CUPS and HPLIP behavior in your environment and alert on deviations such as new outbound network connections from print processes.
Monitoring Recommendations
- Collect endpoint telemetry from Linux hosts running HPLIP and forward process, file, and network events to a centralized analytics platform.
- Track file integrity for HPLIP configuration files under /etc/hp/ and /var/lib/hp/ for unauthorized modifications.
- Review CUPS error logs and HPLIP logs for malformed device URIs or unexpected command-line arguments.
How to Mitigate CVE-2026-91100
Immediate Actions Required
- Apply the vendor-supplied HPLIP updates referenced in the HP Security Bulletin as soon as your distribution makes them available.
- Inventory Linux endpoints, print servers, and workstations that have HPLIP installed and prioritize systems that process untrusted print jobs or device inputs.
- Restrict local access to systems running HPLIP and limit which users can add or configure printers.
Patch Information
HP has remediated the reported issues in updated HPLIP releases. Refer to the HP Security Bulletin for the fixed component versions and update instructions. Linux distribution maintainers typically publish backported packages, so track your distribution's security advisories in parallel.
Workarounds
- Remove or disable HPLIP on systems that do not require HP device support until patches are applied.
- Restrict CUPS administrative interfaces to trusted users and networks to limit who can supply device URIs to HPLIP.
- Run HPLIP-related services under least-privilege accounts and use SELinux or AppArmor policies to constrain command execution.
# Configuration example: remove HPLIP where not required, or update via distro package manager
# Debian/Ubuntu
sudo apt-get update && sudo apt-get install --only-upgrade hplip hplip-data
# Red Hat / Fedora
sudo dnf upgrade hplip hplip-common
# Verify installed version
hp-check -r
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
