CVE-2026-58829 in Android
Summary
by MITRE • 11/02/2026
In fuse_backing_mmap of backing.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.
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Analysis
by VulDB Data Team • 11/02/2026
The vulnerability identified in the Linux kernel's FUSE (Filesystem in Userspace) subsystem specifically affects the fuse_backing_mmap function within backing.c, representing a critical use-after-free condition that poses significant risks to system integrity and security. This flaw arises from improper memory management practices where a pointer is accessed after the memory it references has been freed or returned to the allocator. In the context of FUSE, which allows non-privileged users to implement their own filesystems in user space by interacting with kernel modules, such a defect can be particularly dangerous because it bridges the boundary between untrusted user-space applications and privileged kernel-space operations. The root cause typically involves a race condition or logic error where the lifecycle of an object is not correctly synchronized with its deallocation, leading to scenarios where stale pointers are dereferenced during memory mapping operations.
From a technical perspective, use-after-free vulnerabilities allow attackers to manipulate heap metadata or overwrite adjacent objects in memory by writing through the dangling pointer. In this specific instance within fuse_backing_mmap, an attacker can trigger the allocation and subsequent freeing of certain kernel structures while maintaining access via a previously obtained reference. When the system attempts to map these backing files into user space, it may interact with freed memory regions that have been reallocated for other purposes or contain controlled data injected by the attacker. This mechanism enables arbitrary read/write primitives within the kernel address space, which is the primary requirement for escalating privileges from an unprivileged user account to root-level access without requiring additional execution privileges or complex exploitation chains involving code injection in separate processes.
The operational impact of this vulnerability is severe due to its potential for local privilege escalation with no user interaction required for exploitation beyond having a valid login session on the affected system. An attacker who gains even minimal shell access can exploit this flaw to execute arbitrary code within the kernel context, effectively bypassing all standard security controls such as SELinux or AppArmor if they are not configured to strictly prevent memory corruption exploits. The absence of user interaction requirements means that automated exploitation tools could potentially leverage this weakness against vulnerable systems without needing social engineering tactics or physical access beyond initial network entry points. This makes the vulnerability a high-priority target for threat actors seeking persistent administrative control over compromised hosts, particularly in multi-tenant environments where lateral movement and privilege escalation are critical steps in attack progression.
This flaw aligns with CWE-416, Use After Free, which categorizes errors resulting from accessing memory after it has been freed, leading to unpredictable behavior including crashes or security breaches. Furthermore, the exploitation path corresponds to MITRE ATT&CK techniques related to Privilege Escalation via Kernel Exploitation, specifically leveraging local vulnerabilities to gain higher-level permissions. The lack of user interaction places this in a category of high-severity issues where remote attackers could potentially trigger conditions leading to local compromise if other vectors like network-facing services are present, although the primary vector remains local execution.
Mitigation strategies must focus on immediate patching and rigorous code review practices within kernel development workflows. System administrators should apply vendor-provided security updates that address this specific issue in backing.c as soon as they become available, ensuring that FUSE-related components are updated to versions where memory lifecycle management has been corrected. For environments unable to immediately patch, implementing strict resource limits such as cgroups can help mitigate the impact by restricting the ability of unprivileged users to allocate excessive kernel resources or trigger complex race conditions necessary for successful exploitation. Additionally, enabling Kernel Self-Protection features like KASLR and stack protectors may increase the difficulty of exploiting this vulnerability successfully, although they do not eliminate the underlying flaw. Long-term remediation involves adopting static analysis tools that detect use-after-free patterns during development and enforcing memory safety principles in kernel code to prevent similar defects from being introduced into future releases.