CVE-2026-49414 in FreeBSD
Summary
by MITRE • 06/27/2026
The ELF image activator cleared per-process ASLR preference flags for setuid binaries after the code that computes the PIE base address, rather than before. As a result, a user-requested ASLR disable was still in effect at the point where the base address was chosen.
An unprivileged local user can disable ASLR for a setuid PIE binary by calling procctl(2) before execve(2). This makes exploitation of any separate memory corruption vulnerability in that binary significantly easier.
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Analysis
by VulDB Data Team • 06/27/2026
The vulnerability described represents a critical flaw in the ELF image activation process on FreeBSD systems, specifically affecting how address space layout randomization is handled for setuid binaries. This issue stems from a timing problem in the code execution sequence where ASLR preference flags are cleared after the PIE base address computation has already occurred. The fundamental technical flaw lies in the improper ordering of operations within the kernel's binary loading mechanism, creating a window where user-requested ASLR disablement persists even for setuid processes that should normally maintain their security protections.
The operational impact of this vulnerability is significant for system security, as it undermines one of the primary defenses against memory corruption exploits. When an unprivileged local user invokes procctl(2) to disable ASLR for a setuid PIE binary before execve(2) is called, the system fails to properly enforce the security model that should normally apply to privileged executables. This creates a scenario where attackers can effectively neutralize ASLR protections for critical system binaries, making exploitation of subsequent memory corruption vulnerabilities substantially easier. The vulnerability specifically affects the interaction between user-level process control and kernel-level binary loading mechanisms, creating an unexpected state where privilege escalation opportunities are expanded through seemingly benign process management operations.
This flaw aligns with CWE-1235, which addresses improper handling of security-sensitive data during process execution, and represents a clear violation of the principle of least privilege in operating system design. The vulnerability demonstrates how seemingly isolated kernel subsystems can interact in unexpected ways to create security weaknesses, particularly when dealing with privilege transitions and memory protection mechanisms. From an ATT&CK framework perspective, this issue maps to T1068, which covers "Exploitation for Privilege Escalation," as it provides a method for reducing the security protections that normally defend against privilege escalation attempts.
The mitigation strategy requires addressing the fundamental ordering issue in the kernel's ELF loading code where ASLR flags are cleared at an inappropriate time in the execution sequence. System administrators should ensure all available kernel updates are applied, as this vulnerability is likely to be patched through proper code reordering and validation of ASLR state management. Additionally, monitoring for unusual procctl(2) usage patterns before execve(2) calls can help detect potential exploitation attempts, while maintaining strict enforcement of privilege boundaries in process execution environments. The fix must ensure that ASLR preferences are properly respected for setuid binaries regardless of user-level control requests, maintaining the security invariant that privileged processes cannot have their fundamental protections disabled through user-space operations.
This vulnerability highlights the complexity of modern operating system security where seemingly simple operations can create unexpected interactions between different security mechanisms. The proper implementation requires careful consideration of when and how security policies are enforced during process execution, particularly in scenarios involving privilege transitions and memory protection enforcement. The issue demonstrates that even well-established security features like ASLR can be undermined by subtle timing problems in kernel code execution sequences, emphasizing the importance of rigorous security testing and code review processes for critical system components.