CVE-2026-84233 in Red Hat
Summary
by MITRE • 09/01/2026
A flaw was found in rpm. A local attacker could supply a specially crafted `.gem` filename containing RPM macro syntax. When a user or automated workflow invokes `rpmuncompress -x` on this file, the macro expansion occurs during command construction. This allows the attacker to execute arbitrary commands with the privileges of the invoking account, leading to a compromise of confidentiality, integrity, and availability.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 09/01/2026
The vulnerability identified in the RPM package manager represents a critical security flaw rooted in improper input validation and unsafe handling of user-supplied data during file extraction operations. Specifically, this issue affects the rpmuncompress utility when invoked with the extract flag to process Gem files. The core technical deficiency lies in how the application constructs internal commands for decompression tasks. Instead of treating filenames strictly as static string literals or sanitizing them against executable syntax, the system allows macro expansion within these identifiers. This architectural oversight creates a direct pathway for command injection attacks when an attacker provides a maliciously crafted filename that embeds RPM macro syntax designed to trigger arbitrary code execution upon processing.
From a technical perspective, the exploitation vector relies on the interaction between the file naming convention and the internal logic of rpmuncompress. When a local user or an automated workflow initiates the extraction process by pointing it at a specially constructed .gem file, the utility parses the filename as part of its operational command string. Because RPM macros are designed to expand into various values during package processing, the inclusion of specific macro syntax within the filename causes the system to interpret and execute those commands rather than treating them as literal characters in a path or name. This behavior effectively bypasses standard shell escaping mechanisms that might otherwise prevent such execution, allowing an attacker to inject arbitrary operating system commands directly into the context of the running process.
The operational impact of this vulnerability is severe due to its potential for privilege escalation and full system compromise. Since rpmuncompress typically runs with elevated privileges or within a trusted environment where package management occurs, any command executed via this flaw inherits those same permissions. A local attacker who can place such a crafted file in an accessible directory can trigger the extraction process through various means, including automated build scripts, CI/CD pipelines, or manual user interaction. The successful exploitation leads to a complete compromise of confidentiality, integrity, and availability. Confidentiality is breached as sensitive data may be exfiltrated; integrity is compromised because system files or configurations can be modified arbitrarily; and availability suffers if the injected commands disrupt critical services or delete essential system components.
This vulnerability aligns with CWE-78, which describes Improper Neutralization of Special Elements used in an OS Command commonly known as OS Command Injection. The attack pattern also maps to MITRE ATT&CK technique T1059, specifically sub-techniques related to command and script interpreters like sh or bash, where attackers leverage system utilities to execute malicious payloads. Furthermore, the reliance on local file placement suggests elements of CWE-436, Interpretation Conflict, although the primary mechanism is clearly injection through macro expansion rather than ambiguous parsing alone. The risk is particularly acute in environments that automate package management tasks without strict sandboxing or privilege separation for intermediate tools like rpmuncompress.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. The most effective solution is to apply the vendor-provided patch that updates the RPM package manager to versions where this macro expansion vulnerability has been addressed through stricter input validation and sanitization of filenames before they are passed into command construction logic. Administrators should ensure all systems running affected versions of rpm are updated promptly. In addition to software updates, operational controls such as restricting write access to directories used for temporary file storage or package staging can limit the ability of attackers to place crafted files in locations where automated workflows will process them. Implementing least-privilege principles so that routine extraction tasks do not require root-level permissions further reduces the blast radius should an exploitation attempt succeed. Security monitoring tools should also be configured to detect unusual command execution patterns originating from package management utilities, providing an additional layer of defense against active exploitation attempts.