CVE-2026-50602 in Planet9
Summary
by MITRE • 08/17/2026
A security vulnerability has been identified in Planet9 due to incorrect file permissions assigned to an application executable used by the Planet9 background service. The service runs with SYSTEM privileges, while the affected executable grants excessive permissions to non-administrative users. As a result, an authenticated local user could potentially modify or replace the executable and execute arbitrary code with SYSTEM privileges when the service starts or the system is restarted.
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Analysis
by VulDB Data Team • 08/17/2026
The identified vulnerability in Planet9 represents a critical privilege escalation flaw rooted in improper file permission configuration for application executables managed by background services. This specific issue arises from an incorrect assignment of access control lists to binary files that are invoked by the Planet9 service, which operates under high-privilege SYSTEM accounts. The core technical failure lies in granting write or modify permissions to non-administrative users on these executable binaries. In a secure operating system environment, executables associated with privileged services must be strictly protected against modification by standard user accounts to prevent unauthorized changes to the code that runs at kernel-level authority. By allowing lower-privileged entities to alter these files, the security boundary between untrusted user space and trusted system space is effectively bypassed through file manipulation rather than direct exploitation of a logic flaw in the service itself.
From an operational perspective, this misconfiguration enables authenticated local users to perform arbitrary code execution with SYSTEM privileges without requiring additional elevation steps or exploiting complex memory corruption bugs. An attacker who gains access to the machine as a standard user can simply replace the legitimate executable with a malicious payload containing their own shellcode or command-line instructions. When the Planet9 background service subsequently starts, restarts, or is triggered by system events such as boot-up, it loads and executes this compromised binary under its existing SYSTEM context. This results in immediate full control over the operating system, allowing the attacker to install backdoors, steal sensitive data, modify security configurations, or pivot to other systems within the network infrastructure. The impact is severe because it circumvents traditional authentication mechanisms by leveraging trusted service behavior against itself.
This vulnerability aligns with CWE-732, which describes incorrect permission assignment for Critical Privileged Function, and specifically relates to CWE-250 regarding execution with unnecessary privileges where the software does not properly restrict permissions. In terms of adversary tactics, this scenario maps directly to ATT&CK technique T1068 Exploitation for Privilege Escalation, as well as T1034 Process Injection or T1574 Hijack Execution Flow if the attacker modifies dynamic link libraries alongside executables. The attack vector is classified as Local (T1059) with Authentication required (T1078), indicating that physical or remote authenticated access to a standard user account on the affected system is sufficient for exploitation, making it particularly dangerous in shared computing environments or multi-tenant systems where privilege separation is expected but not enforced correctly.
Mitigation strategies must focus immediately on correcting file system permissions and implementing robust defense-in-depth measures. Administrators should audit all executables associated with high-privilege services to ensure that only the SYSTEM account, Local Service accounts, and explicitly defined administrators have write or modify access rights; standard users should be restricted to read-only execution permissions if necessary for functionality. Implementing mandatory integrity control policies can further restrict low-integrity processes from writing to high-integrity objects like system executables. Additionally, deploying application whitelisting solutions such as Windows AppLocker or Microsoft Defender Application Control will prevent unauthorized binaries from executing regardless of file permission settings. Regular auditing using tools that monitor changes to critical system directories and service configurations is essential to detect any future attempts at privilege escalation via this vector before they can be fully exploited by malicious actors.