CVE-2026-58826 in Android
Summary
by MITRE • 11/02/2026
In ksys_unshare of fork.c, there is a possible memory corruption due to a use after free. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 11/02/2026
The vulnerability identified in the Linux kernel function ksys_unshare within fork.c represents a critical security flaw characterized by a use-after-free condition that can result in memory corruption and subsequent local privilege escalation. This specific defect arises during the process of unsharing user resources, where the kernel fails to properly manage the lifecycle of certain data structures after they have been freed or detached from their active context. When an attacker triggers this code path through system calls associated with resource isolation such as clone or unshare operations, the kernel may attempt to access memory that has already been released back to the allocator pool. Because modern operating systems often reuse freed memory for new allocations without clearing it immediately, accessing stale pointers can lead to reading sensitive information from other processes or writing data into unintended memory regions controlled by different entities within the system.
From a technical perspective, this use-after-free scenario is classified under CWE-416 which denotes using an incorrect reference after deallocation. The root cause typically involves race conditions or logic errors where references to kernel objects are not invalidated immediately upon freeing them. In the context of fork.c and ksys_unshare, the complexity lies in managing shared memory segments, namespaces, and file descriptors across process boundaries. If a pointer is retained by one part of the kernel while another part frees the underlying object, subsequent operations on that pointer will operate on potentially reclaimed or repurposed memory. This lack of proper reference counting or synchronization mechanisms allows an unprivileged user to manipulate kernel state in ways that were not intended by the developers, effectively bypassing standard security boundaries enforced at the process level.
The operational impact of this vulnerability is severe due to its potential for local escalation of privilege with no additional execution privileges needed and without requiring any form of user interaction. An attacker who gains access to a low-privileged shell account can exploit this flaw to execute arbitrary code within the kernel space, thereby gaining root-level permissions over the entire system. This capability allows the compromise of confidentiality, integrity, and availability for all data stored on the affected machine. Since no user interaction is required, automated exploitation tools can leverage this vulnerability remotely if network services expose vulnerable interfaces or locally via any authenticated session. The absence of a need for complex social engineering or physical access makes this a high-risk vector for persistent backdoors and lateral movement within compromised networks.
To mitigate this risk, system administrators should apply the latest security patches provided by their Linux distribution vendors which address the memory management logic in fork.c. It is crucial to monitor kernel updates closely as these fixes often involve rigorous code reviews to ensure that all pointers are nullified after free operations and that reference counts are accurately maintained during resource unsharing procedures. Additionally, deploying runtime protection mechanisms such as Kernel Self-Protection Project (KSP) features like KASLR for address space layout randomization can make exploitation more difficult by obscuring the location of kernel structures. Enforcing strict MAC policies using SELinux or AppArmor further limits the potential damage even if an exploit succeeds by restricting what actions a compromised process can perform within the user namespace context. Regular auditing of system calls and monitoring for anomalous behavior related to resource unsharing activities can also aid in early detection of exploitation attempts aligned with ATT&CK techniques involving privilege escalation through kernel vulnerabilities.