CVE-2026-63404 in Faktory
Summary
by MITRE • 08/26/2026
Faktory is a language-agnostic background job server. In versions prior to 1.10.0, the embedded Redis bootstrapper is vulnerable to an insecure temporary file flaw that lets a local unprivileged user hijack the Redis configuration and escalate to root. It writes its startup configuration to a fixed, predictable, world-writable path, /tmp/redis.conf, only creating the file if it does not already exist and never validating it on later boots. Because /tmp is world-writable, a local unprivileged user can pre-create /tmp/redis.conf with attacker-chosen Redis directives before Faktory starts, and Faktory will use the planted file verbatim. Faktory only overrides the unixsocket, dir, and logfile options, leaving directives such as bind, protected-mode, requirepass, and loadmodule attacker-controlled. This lets an attacker silently expose the entire job queue over an unauthenticated network port with no visible error to the administrator. Because the official systemd unit runs Faktory, and the redis-server child it spawns, as root, an attacker can also supply a loadmodule directive to execute arbitrary native code in the root-owned Redis process, escalating from a local unprivileged user to root. This issue is fixed in version 1.10.0.
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Analysis
by VulDB Data Team • 08/26/2026
The vulnerability identified in Faktory versions prior to 1.10.0 represents a critical insecure temporary file creation flaw within its embedded Redis bootstrapper mechanism. As a language-agnostic background job server, Faktory relies on an internal instance of the Redis database engine to manage task queues and state. During initialization, this component attempts to write its startup configuration to a fixed path located at /tmp/redis.conf. The core technical deficiency lies in the file creation logic, which employs a check-if-exists pattern without utilizing secure temporary file practices such as O_EXCL or mkstemp. This approach allows any local user with standard unprivileged access to pre-create this specific file before Faktory initiates its boot sequence. Since the /tmp directory is universally writable on most Unix-like operating systems, an attacker can easily place a maliciously crafted configuration file at this predictable location, effectively hijacking the initialization process of the embedded Redis server without triggering any immediate error or warning from the application.
The operational impact of this flaw extends beyond simple configuration manipulation to severe privilege escalation and data exposure risks. Because Faktory only overrides specific directives such as unixsocket, dir, and logfile during its startup routine, all other Redis configuration parameters remain under the control of whoever created the /tmp/redis.conf file. This oversight allows an attacker to inject critical commands that alter the security posture of the database instance. Specifically, by setting the bind directive, an attacker can force the embedded Redis server to listen on a network interface rather than just a local socket. By disabling protected-mode and omitting requirepass directives, the attacker ensures that this newly exposed port accepts connections from any remote host without authentication. Consequently, the entire job queue becomes accessible to external actors, leading to potential data leakage, unauthorized task execution, or denial of service through queue manipulation.
The severity of this vulnerability is further amplified by the deployment context in which Faktory typically operates. The official systemd unit file for Faktory executes both the main application and its spawned redis-server child process with root privileges. This architectural decision means that any code executed within the Redis environment runs with the highest level of system access. An attacker who has successfully planted a malicious configuration can exploit this by including a loadmodule directive in /tmp/redis.conf. If Faktory loads a shared object specified by this directive, and if an attacker controls or influences the loading path, they may achieve arbitrary code execution within the root-owned Redis process. This effectively transforms a local unprivileged user account into full system compromise, allowing for complete control over the host machine. The lack of visible errors during boot means that administrators remain unaware of the breach until malicious activities are observed in logs or network traffic.
From a classification perspective, this vulnerability aligns with CWE-377, which describes insecure temporary file creation, and CWE-250, indicating execution under unnecessary privileges due to improper configuration handling. In terms of offensive security frameworks, it maps directly to ATT&CK technique T1496, Resource Hijacking, where an attacker uses system resources for their own purposes, as well as techniques related to privilege escalation via process injection or module loading such as T1055 if dynamic library manipulation is involved. The failure to validate configuration inputs against a whitelist of allowed parameters also reflects CWE-20, Improper Input Validation, specifically regarding the lack of sanitization on file contents used for system initialization.
To mitigate this vulnerability and prevent similar issues in future deployments, it is imperative that organizations upgrade Faktory to version 1.10.0 or later, where the embedded Redis bootstrapper has been patched to use secure temporary file creation methods. For environments running older versions that cannot be immediately updated, administrators should ensure that no unprivileged users have write access to /tmp/redis.conf if it exists, although this is difficult to enforce reliably due to the nature of shared temp directories. A more robust mitigation involves reviewing systemd unit files to avoid running application components as root unless absolutely necessary; applying principle of least privilege by creating a dedicated service account for Faktory and its Redis child process would significantly reduce the impact of any successful exploitation attempt. Additionally, implementing strict file integrity monitoring on critical configuration paths can help detect unauthorized modifications before they are utilized during system startup.