CVE-2011-4356 in Celery
Summary
by MITRE
Celery 2.1 and 2.2 before 2.2.8, 2.3 before 2.3.4, and 2.4 before 2.4.4 changes the effective id but not the real id during processing of the --uid and --gid arguments to celerybeat, celeryd_detach, celeryd-multi, and celeryev, which allows local users to gain privileges via vectors involving crafted code that is executed by the worker process.
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Analysis
by VulDB Data Team • 11/27/2021
The vulnerability identified as CVE-2011-4356 represents a critical privilege escalation issue affecting Celery message queue systems across multiple versions. This flaw specifically targets the handling of user and group identifier arguments during process initialization, creating a discrepancy between effective and real user identifiers that malicious actors can exploit to elevate their privileges. The affected versions include Celery 2.1 and 2.2 before 2.2.8, 2.3 before 2.3.4, and 2.4 before 2.4.4, indicating a widespread impact across the Celery ecosystem during this period. The vulnerability manifests through the improper management of --uid and --gid command line arguments when executing key Celery components including celerybeat, celeryd_detach, celeryd-multi, and celeryev processes.
The technical root cause of this vulnerability lies in the improper implementation of privilege management within the Celery worker processes. When users specify --uid and --gid arguments to modify the user and group identifiers for Celery processes, the system correctly updates the effective user identifier but fails to properly change the real user identifier. This creates a security boundary that can be exploited by local attackers who craft malicious code designed to be executed by the worker process. The mismatch between effective and real identifiers allows attackers to potentially execute code with elevated privileges beyond what was initially intended, as the system's privilege checking mechanisms rely on the real user identifier for validation. This vulnerability directly maps to CWE-250, which addresses "Execute Code with Unintended Elevated Privileges" and aligns with ATT&CK technique T1068, which covers "Exploitation for Privilege Escalation" by leveraging process manipulation vulnerabilities.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it can enable attackers to gain unauthorized access to system resources and potentially compromise entire infrastructure components. Local users with access to the system can exploit this weakness to execute malicious code with higher privileges, potentially leading to complete system compromise. The attack vector specifically involves crafting code that gets executed by the worker process, making this particularly dangerous in environments where Celery workers process untrusted input or where multiple users share system resources. This vulnerability undermines the fundamental security model of process isolation and privilege separation that is essential for maintaining system integrity in distributed computing environments.
Mitigation strategies for CVE-2011-4356 should prioritize immediate patching of affected Celery versions to ensure proper handling of user and group identifiers. Organizations should implement strict access controls and privilege separation measures, ensuring that Celery processes run with the minimum necessary privileges. Additionally, system administrators should conduct thorough audits of all Celery installations to verify proper privilege management and implement monitoring for unauthorized privilege escalation attempts. The fix for this vulnerability involves ensuring that both effective and real user identifiers are properly updated during process initialization, preventing the discrepancy that enables privilege escalation. Security teams should also consider implementing runtime protection mechanisms and regular security assessments to identify similar privilege management flaws in other system components that may be susceptible to similar exploitation techniques.