CVE-2026-91104 in Linux Imaging and Printing Software
Summary
by MITRE • 09/16/2026
HP has identified and remediated multiple externally reported vulnerabilities within HPLIP. The findings affect several software components that could potentially enable remote code execution, privilege escalation, denial of service, information disclosure, or unauthorized file modification under certain conditions.
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Analysis
by VulDB Data Team • 09/16/2026
Hewlett-Packard has addressed a cluster of security flaws identified in the HP Linux Imaging and Printing (HPLIP) suite, resolving issues reported by external researchers that pose significant risks to system integrity and confidentiality. These vulnerabilities span multiple software components within the HPLIP ecosystem, which serves as the primary driver interface for many HP printers on Linux-based operating systems. The remediation effort targets a range of critical failure modes including remote code execution, privilege escalation, denial of service, information disclosure, and unauthorized file modification. Given that HPLIP often runs with elevated privileges to manage hardware interfaces and print queues, these flaws present a high-risk attack surface for attackers seeking to compromise host systems through peripheral devices or network-accessible printing services.
The potential for remote code execution represents the most severe threat among the identified vulnerabilities. In many implementations of printer driver suites like HPLIP, complex parsing logic is required to interpret proprietary binary formats and command sets sent from client machines over local networks or USB connections. If input validation mechanisms are insufficient, an attacker could craft malicious print jobs containing specially crafted data structures that exploit buffer overflow conditions or improper memory handling routines within the application. Successful exploitation of these flaws would allow a remote adversary to execute arbitrary code with the privileges granted to the HPLIP process, which frequently includes root-level access for hardware configuration and spooler management. This capability effectively bypasses standard operating system security boundaries, granting full control over the affected host machine without requiring user interaction beyond sending a malicious print request or packet sequence.
Privilege escalation vulnerabilities further exacerbate the risk profile by allowing lower-privileged users to gain administrative rights on the target system. These flaws typically stem from improper permission checks during file operations or configuration updates initiated through the HPLIP interface. For instance, if the application fails to verify ownership or access controls when writing temporary files or updating printer configurations in shared directories like /tmp or spooler queues, a local user could manipulate these resources to overwrite critical system binaries or scripts with malicious content. When the privileged HPLIP process subsequently executes or loads these modified files, it inadvertently runs attacker-controlled code as root. This mechanism enables persistent access and deepens the impact of any initial compromise, allowing attackers to install backdoors, modify security policies, or pivot to other systems within the network infrastructure.
Denial of service conditions arise from flaws that cause the HPLIP services or associated daemon processes to crash when processing malformed input data. While less severe than code execution in terms of direct system takeover, these vulnerabilities can disrupt critical business operations by rendering printing capabilities unavailable. Attackers may exploit memory corruption errors such as use-after-free or integer overflows during the parsing of large print files or specific PCL/PostScript commands to trigger segmentation faults or infinite loops within the processing threads. This results in service unavailability for all users relying on the affected printer, impacting productivity and potentially masking more sophisticated attacks by drawing attention away from subtle indicators of compromise such as network anomalies or minor log entries that might otherwise go unnoticed during a prolonged intrusion attempt.
Information disclosure vulnerabilities expose sensitive system data to unauthorized parties through improper handling of error messages, debug logs, or memory contents. Flaws in how HPLIP processes and returns status information can leak details about the underlying operating system version, installed software configurations, network topology, or even user credentials if they are inadvertently included in diagnostic output. Additionally, buffer over-read conditions may allow attackers to retrieve arbitrary memory contents from the process space, potentially exposing cryptographic keys used for secure printing protocols or session tokens that authenticate users to print management interfaces. This leakage of intelligence facilitates further reconnaissance efforts and lowers the barrier for subsequent exploitation stages by providing precise details about the target environment's security posture and configuration weaknesses.
Unauthorized file modification capabilities allow attackers to alter system files outside of intended application boundaries, potentially leading to persistent compromise or data integrity violations. These flaws often result from insecure temporary file creation practices where predictable filenames are used without proper locking mechanisms or atomic operations. An attacker monitoring these directories can predict the location of newly created temporary files and race condition attacks may enable them to replace legitimate files with malicious equivalents before HPLIP processes them. This vector is particularly dangerous in multi-user environments where multiple users share access to printing services, as it allows a single compromised account to affect system-wide stability or inject malware into shared resources that are subsequently executed by privileged processes belonging to other users or the root user.
Mitigation strategies must prioritize immediate patching of all affected HPLIP components using vendor-provided updates that address these specific input validation and permission control flaws. Organizations should verify their Linux distribution repositories for updated packages that incorporate HP's security fixes, ensuring that both the core driver libraries and associated management utilities are brought to secure versions. In environments where updating is not immediately feasible, network segmentation strategies can limit exposure by restricting access to printing services only from trusted subnets or specific user groups. Additionally, implementing strict file system permissions on directories used for temporary storage and spooling reduces the risk of race condition attacks and unauthorized modifications. Security teams should also monitor logs for unusual patterns in print job submissions or unexpected process terminations that may indicate exploitation attempts against these vulnerabilities before patches are applied.
The technical nature of these flaws aligns with common weakness categories defined by industry standards, particularly CWE-120 Buffer Copy without Checking Size of Input which underlies many remote code execution scenarios, and CWE-732 Incorrect Permission Assignment for Critical Resource related to privilege escalation and file modification issues. From a tactical perspective, the exploitation vectors correspond to MITRE ATT&CK techniques such as T1203 Exploitation for Client Execution via malicious print jobs or scripts, and T1059 Command and Scripting Interpreter if script-based components are leveraged during post-exploitation phases. Understanding these mappings helps security operations centers prioritize detection rules based on known indicators of compromise associated with printer driver exploitation campaigns. Continuous monitoring of vendor advisories remains essential as new variants or related flaws in dependent libraries may emerge, requiring ongoing vigilance to maintain the integrity and availability of printing infrastructure within enterprise networks.